THE STAR FORMATION NEWSLETTERAn electronic publication dedicated to early stellar/planetary evolution and molecular clouds

No. 240 — 9 December 2012 Editor: Bo Reipurth (reipurth@ifa.hawaii.edu)

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The Star Formation Newsletter

Editor: Bo Reipurthreipurth@ifa.hawaii.edu

Technical Editor: Eli Bresserteli.bressert@csiro.au

Technical Assistant: Hsi-Wei Yenhwyen@asiaa.sinica.edu.tw

Editorial Board

Joao AlvesAlan Boss

Jerome BouvierLee Hartmann

Thomas HenningPaul Ho

Jes JorgensenCharles J. Lada

Thijs KouwenhovenMichael R. Meyer

Luis Felipe RodrıguezEwine van Dishoeck

Hans Zinnecker

The Star Formation Newsletter is a vehicle forfast distribution of information of interest for as-tronomers working on star and planet formationand molecular clouds. You can submit materialfor the following sections: Abstracts of recentlyaccepted papers (only for papers sent to refereedjournals), Abstracts of recently accepted major re-views (not standard conference contributions), Dis-sertation Abstracts (presenting abstracts of newPh.D dissertations), Meetings (announcing meet-ings broadly of interest to the star and planet for-mation and early solar system community), NewJobs (advertising jobs specifically aimed towardspersons within the areas of the Newsletter), andShort Announcements (where you can inform or re-quest information from the community). Addition-ally, the Newsletter brings short overview articleson objects of special interest, physical processes ortheoretical results, the early solar system, as wellas occasional interviews.

Newsletter Archivewww.ifa.hawaii.edu/users/reipurth/newsletter.htm

List of Contents

Editorial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Interview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

My Favorite Object . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Perspective . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Abstracts of Newly Accepted Papers . . . . . . . . . . 13

Abstracts of Newly Accepted Major Reviews . 50

Dissertation Abstracts . . . . . . . . . . . . . . . . . . . . . . . . 52

New Jobs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

New and Upcoming Meetings . . . . . . . . . . . . . . . . . 57

New Books . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

Short Announcements . . . . . . . . . . . . . . . . . . . . . . . . 61

Cover Picture

The L1630, or Orion-B, cloud is located just abovethe Orion Belt stars. The northern part, seen here,hosts the two bright reflection nebula NGC 2068and 2071, as well as a rich population of young low-mass stars. At a distance of only about 400 pc, theL1630 cloud permits detailed studies of individualobjects. Prominent in the dense and highly struc-tured cloud in the southern part of the image is theHH 24 complex, harboring half a dozen outflows, aswell as numerous other Herbig-Haro objects. Nearthe center of the image one sees the bright compactreflection nebula known as McNeil’s Nebula, illu-minated by the FUor event in V1647 Ori that tookplace in late 2003.

Image courtesy Ignacio de la Cueva Torregrosa

Submitting your abstracts

Latex macros for submitting abstractsand dissertation abstracts (by e-mail toreipurth@ifa.hawaii.edu) are appended toeach Call for Abstracts. You can alsosubmit via the Newsletter web inter-face at http://www2.ifa.hawaii.edu/star-formation/index.cfm

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Editorial

This issue is no. 240, and with it we can celebrate 20 years of publication of the Star Formation Newsletter.

Twenty years ago the world looked different, as we were only at the beginning of the information age and, especiallyfor young people, it may be difficult to understand that information was not so easy to get hold of as it is today.At that time many institutes still printed preprints and mailed them to other institutes. The process of publishing apaper was much slower, and people actually went to the library and (gasp) read the journals as they came in.

It was in that environment that the Star Formation Newsletter was launched as the first electronic newsletter inastronomy. This soon led to more such newsletters being circulated, most of which unfortunately had short lives,although some still exist. The Star Formation Newsletter thus filled a clear need for rapid dissemination of abstractsof new papers, as well as other information of interest to the star formation community, like dissertation abstracts,announcement of meetings and new jobs, and the occasional book review.

Today, twenty years later, the need for the Star Formation Newsletter is not so obvious. We are now connected to theinternet 24 hours a day, and in a sense we have the opposite problem of trying to keep the avalanche of information atbay. The limiting factor today is to find only the information that we need, and to find time to digest that information.

Electronic preprint servers, especially arXiv, now offer a daily dosis of new papers with the latest results, and this haschanged the way we work. It has also been a great democratic force, since to get the latest news it no longer mattersif a researcher or student is working in USA or Uganda.

With this in mind I therefore felt that it was time to close the Star Formation Newsletter. However, whenever Imentioned this to colleagues, I was always met with a ’Please don’t do that’. A lot of people have responsibilities thatdo not allow them time to browse around for potentially interesting information, and instead they take time once amonth to look at the Newsletter to review the state of the field.

Since the option of just continuing the Newsletter in its present form was not really meaningful, and after somesoul-searching, I decided to upgrade the Newsletter, taking advantage of the developments in technology over the pasttwenty years. Hence you now see here an issue of the Newsletter that has color pictures, and hyperlinked URLs afterthe abstracts. And I have also introduced interviews as well as small articles (My Favorite Object and Perspective),which give an expert’s view on a given object or subject. These were inspired by the fact that in recent years thegrowth in subscribers to the Newsletter has been almost exclusively among students and postdocs. This is because,with about 1300 subscribers, almost everybody in the star formation community gets the Newsletter, and the onlygrowth is among the new generation of researchers.

It has always been a puzzle to me that I only receive about 50% of the abstracts of relevant papers. Given that weall publish to be read, it seems logical that after spending many months to prepare research results for publicationone should also spend 5 minutes to circulate an abstract to potential readers. I therefore urge readers to submit theirabstracts in the spirit of a shared community. If we all do this, we all can benefit from a near-complete monthlycompilation. The Newsletter is a creation of the star formation community for the star formation community.

With a new Technical Editor, Eli Bressert, and a new Technical Assistant, Hsi-Wei Yen, we have started along twopaths for the Newsletter. Eli is working on software that will automatically extract abstracts from the journals aspapers appear in electronic form. This will take some time, and meanwhile Hsi-Wei is helping me to extract missingabstracts from astro-ph. Until the software is in place, please continue to submit your abstracts.

The focus of the Newsletter will remain towards Galactic star formation; abstracts on extragalactic star formation willonly be brought if they deal with studies in the Magellanic Clouds and the very nearest Local Group galaxies. We willno longer bring abstracts on the more tenuous interstellar medium, except when directly relevant to star formation.We are now seeing a lot more studies of planet formation, making this one of the most vibrant areas at the momentand reflecting the changes that our field has undergone in the past twenty years.

Bo Reipurth

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Richard B. Larsonin conversation with Hans Zinnecker

Q: Your 1968 dissertation was entitled “Dynamics of aCollapsing Protostar”, and it was a pioneering study. Whatled you to do a thesis on that topic, and what was the in-fluence of your thesis advisor, Guido Munch?

A: As an undergraduate at the University of Toronto Ifirst became interested in astronomy, like many students,for philosophical reasons: I wanted to know the answers tothe big questions about the universe, and I realized that Iwould have to learn some astronomy to answer them. Asa graduate student at Caltech I was fascinated by galaxiesand wanted to understand how they formed. My first ideafor a thesis project was to calculate how a spherical galaxyforms, using a simple treatment of star formation. WhenI discussed this idea with Maarten Schmidt, he seemeddubious about it as a thesis project and suggested that Italk with Guido Munch, who knew more about interstel-lar matter and star formation. Guido was also skepticalabout my grandiose ideas, and he said “before you tryto understand how a galaxy forms, why don’t you try tounderstand how one star forms?” I quickly realized thatGuido was right and that this would be a better thesistopic, although still challenging. But I decided to give it atry because I had already read nearly everything that hadbeen written about star formation (which was not so muchin those days), and I had also gained some experience incalculating stellar structure working with Pierre Demar-que in Toronto. So I plunged into the project, not havingany idea how far I would get with it. Guido again providedcrucial advice at a later stage when I realized that I wouldhave to deal with an accretion shock at the surface of thestellar core, and I proposed to include a treatment of ra-diative transfer in the vicinity of the shock. Guido said“no, don’t waste your time with that, try using a simpleapproximation”, and this gave me the idea that I shouldtry to find a simple approximation that would allow me tocontinue my protostar calculation. I eventually came up

with an approximation that seemed adequate, and it didthe job and allowed me to calculate all the way through toa pre-main sequence star on the Hayashi track. After thiswork was published my treatment of the accretion shockwas controversial, but eventually more detailed treatmentsshowed that it had not introduced a serious error.

Q: What do you think were the key findings of this work?

A: Looking back, I think that the most important result ofthat work might have been the very first one that I foundwhen I got my first collapse code working. I had writtena simple code to calculate isothermal collapse, and thefirst successful run with it showed the runaway growth ofa sharp central peak in density that appeared to be ap-proaching a singularity. This result was not what anyonehad expected, and it was also to prove controversial, butI eventually convinced myself that it was at least qualita-tively correct and found a similarity solution showing thisbehavior. At about the same time, Michael Penston foundsimilar results and independently derived the same simi-larity solution. This ‘Larson-Penston solution’, as it hasbeen called, was perhaps the most enduring result of thatearly work, and it has been shown to have much greatergenerality. This basic qualitative result led to a changein thinking about star formation by showing that starformation begins with the runaway formation of a near-singularity in density, and then continues as an accretionprocess. Once you adopt the view that star formation islargely an accretion process, you can calculate many thingsabout it by studying how the accretion process works.

Q: You were among the first to suggest that most, if notall, stars are born in small multiple systems. How do yousee that subject today, and how important is it to our un-derstanding of star formation?

A: Binary and multiple systems are clearly the normal waythat nature makes stars, and most single stars are prob-ably escapers from such systems. From a general pointof view this is completely unsurprising because nature iscomplex, and star-forming clouds in particular are highlycomplex and have structure and motions on all scales.This has major implications for our understanding of starand planet formation because it means that most starsform in close proximity to other stars, and therefore thatinteractions will almost certainly play an important rolein their formation. Our Sun and Solar System may not betypical, and indeed recent studies have found an enormousdiversity in extra-solar planetary systems. The fact thatstar-forming clouds quickly become highly structured onall scales, probably because of both turbulence and self-gravity, means that their dynamics must necessarily behighly chaotic. To me this is a lesson that we as theo-rists have to respect the diversity and complexity and un-predictability of nature and be very cautious in applyingsimple theoretical models.

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Q: Thirty years ago you suggested the existence of scalingrelations for molecular clouds linking velocity dispersionand density with size. What is your current view of these“Larson relations”?

A: There are real trends like the ones I discussed, but ithas to be kept in mind that they are only broad correla-tions with a lot of scatter, and that different studies canfind different results. These relations have been endlesslydebated and I think they have often been overinterpreted.What is clear is that the internal motions in molecularclouds are very complex and that they are at least in parthierarchically structured like turbulence. But these factsare not diagnostic of any particular origin for these mo-tions, or of any particular mechanism for sustaining them.Even the basic energy source is still debated, sometimesheatedly. Probably all of the suggested mechanisms con-tribute at some level. The main implication of all thisfor star formation is that the initial conditions for it arelikely to be characterized by chaotic supersonic motions ona range of scales, and therefore that idealized models maynot be relevant. But once gravity takes over, as it musteventually if stars are to form, gravitational dynamics be-comes increasingly dominant and develops characteristicsof its own that become independent of the initial condi-tions. For example, the properties of binary and multiplesystems, and perhaps even planetary systems, may dependmore on the universal properties of gravitational dynamicsthan on the initial state of star forming clouds.

Q: Ten years ago you wrote an influential paper on “TheRole of Tidal Interactions in Star Formation”. What wereyour key points?

A: I had earlier suggested that gravitational torques indisks are likely to play an important role in star forma-tion, and in the paper you mention I suggested that tidalinteractions between stars and disks in a system of form-ing stars could also be important for redistributing angularmomentum and thus helping to solve the angular momen-tum problem. Recent detailed simulations of star forma-tion do indeed show strong gravitational interactions be-tween stars and disks, sometimes to the extent that disksare completely disrupted. What seems clear is that gravitymust often be an important player in the dynamics of disksand in the redistribution of angular momentum. Mag-netic and thermal pressure forces can be equally impor-tant, and many interesting phenomena probably involve acomplex interplay of forces. But non-radial gravitationalforces alone can already go a long way toward solving theclassical ‘angular momentum problem’, in which case thisproblem can be seen as being at least in part just an arti-fact of oversimplified models. This is another case of thecomplexity of nature not being fully appreciated in earlywork.

Q: You have also been interested for a long time in the

properties and origin of the stellar Initial Mass Function.What is your current view of this subject?

A: I have been interested in the stellar IMF from the be-ginning of my career because I was always surrounded bypeople who wanted me to explain the IMF. So I made anumber of attempts over the years based on various ideas,and I have tried to keep up with the observational statusof the subject. The main thing I have learned after allthese years is that when looked at in any detail, this sub-ject is a can of worms. In general terms, we know thatfor massive stars the IMF looks something like a powerlaw, perhaps not too different from that originally pro-posed by Salpeter, and that at the low end the IMF showsa turnover below one solar mass. Whether any feature ofthe IMF is universal has been debated inconclusively fordecades, and the subject has a long history of claims thatdidn’t stand the test of time. On the observational side,it is clear that sample definition is of critical importance,but in the end arbitrary choices always have to be madeabout what to include in the sample. Theorists then haveto be careful to theorize about what the observers actuallyobserved if they want their work to be relevant. Observershave learned from hard experience to pay careful attentionto sample selection, but theory isn’t there yet. Concern-ing the physics behind the IMF, I have found appealingthe idea that the low-mass turnover is determined by fun-damental atomic physics through the thermal propertiesof star-forming clouds. It seems clear that the thermalphysics is indeed important, but other effects can also beimportant, and we don’t yet have a full understanding ofthe origin of the IMF and can’t yet make the predictionsthat observers would like us to make, for example howthe IMF might vary in different circumstances. What’sneeded is big simulations that include as much of the rel-evant physics as possible, but this is difficult work.

Q: Computational star formation has made amazing stridessince you began your work almost 50 years ago. What doyou see as the main challenges today, and where do youthink this field is heading?

A: See above for some of the challenges. I don’t wantto predict where this field is heading, but continuing ad-vances in hardware and software will surely continue tomake bigger and better calculations possible. I hope thatenterprising young people will continue to push ahead withsuch calculations. But it will require a large effort andexpertise in a range of areas of astrophysics and compu-tation, and big projects will have to be organized. I hopeI live to see many more advances, but I wouldn’t attemptto predict what they will be. It will be an adventure tofind out.

Q: What are you planning to do in your retirement?

A: Less astronomy and more of everything else.

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My Favorite ObjectKH 15D:

The Gift that Keeps on Giving

William Herbst

In 1995, during a time domain study of the young clusterNGC 2264 with a small telescope on the campus of Wes-leyan University, my student Kristin Kearns and I discov-ered a variable star with unique and puzzling behavior. Itwas strictly periodic on a 48.37 d cycle, much longer thanthe rotation period of a typical T Tauri star, and hadan amplitude of several magnitudes, much larger than isnormally seen for young stars. It appeared to be under-going regular eclipses, but in the middle of each eclipseit would briefly return to near full brightness or, in onecase, above full brightness and then quickly fade back tominimum light. We described the behavior in a coupleof paragraphs buried in a paper on the rotation proper-ties of the cluster stars (Kerans & Herbst 1998). Laterinvestigations Winn et al. 2003, Johnson & Winn 2004,Maffei, Ciprini & Tosti 2005) would show that the star,which had first been noticed as a variable by Badalian &Erastova (1970) and given the variable star designationV582 Mon, appeared generally brighter and significantlyless variable during the 1960’s through early1980’s, withno evidence of eclipse behavior. An unfortunate gap in thehistoric record from 1982 to 1995, caused by the phase-outof photographic plate-based surveys, makes it uncertain asto exactly when the deep eclipse phase began.

As we continued to monitor the star at Van Vleck Ob-servatory during the subsequent seasons its behavior be-came ever more intriguing. The duration of the eclipsephase continued to grow and the brightness turnaroundnear mid-eclipse became smaller and smaller. Few starshave light curves that evolve in such steady, secular fash-ion and none had ever shown the particular characteristicsof this enigmatic object. The first phase of intense work onthe star began, aimed at unraveling the mystery of what

could cause such bizarre behavior. Another Wesleyan stu-dent, Catrina Hamilton, took up the work as part of herPhysics Ph.D. thesis. We learned that the star showedlittle, if any, change in spectral class when in eclipse andthat the duration and depth of the eclipses continued togrow, from ∼3 mag and 16 days in 1996 to ∼3.5 mag and20 days by 2002. Low resolution spectra revealed the starat maximum brightness as a K7 dwarf or sub-giant withstrong Li I absorption and weak Hα emission – an ordinaryweak-line T Tauri star. The only dramatic spectral changeduring eclipse was an increase in equivalent width of theHα emission from 2 A to 30-50 A, and a strengthening ofthe [OI] and [SII] lines coming from a weak jet. The starwas evidently a low mass (∼0.5 M⊙), pre-main sequencemember of NGC 2264 that was still weakly accreting andbeing eclipsed on a 48.37 d period by something muchlarger than a companion star, and possibly growing bythe year! The only interpretation that made any sense tous was that the eclipsing object was part of the circum-stellar disk that must still be present to account for theaccretion and jet activity.

Its uniqueness and potential importance to star and planetformation gained KH 15D some visibility at conferencesand with the press. A New York Times article was re-portedly the spur for some work by astronomers outsideour little group at Wesleyan. Various theories were pro-posed, including the formation of an anti-cyclonic vortexof grains in a circumstellar disk that could remain stablefor many rotations and possibly function as the eclips-ing body (Barge & Viton 2003). Agol et al. (2004) pro-posed that the star was surrounded by a warped disk or-biting as a solid body and that the periodic passage of thewarp across our line of sight was responsible for the eclipsebehavior. The landscape changed dramatically, however,with the predictions (independently and roughly simulta-neously) by Chiang & Murray-Clay (2004) and Winn etal. (2004) that KH 15D was a binary system. This wasquickly confirmed by a Keck/HIRES radial velocity study(Johnson et al. 2004). The 48.37 d period was recognizedas the orbital period of the binary, which was believed toconsist of two rather similar stars in a fairly eccentric (e ∼0.6) orbit. While in this version of the story it is the starsthat orbit, not a feature in a circumstellar disk around asingle star, it is still nonetheless the disk that is responsi-ble for the eclipses. More precisely, we should say that theocculting body is an inner, dynamically-independent ring,within the accretion disk. The main difference is that inthe binary model, the occulting feature is at much largerdistances from the star(s), roughly 1-5 AU, rather thannear 0.1 AU, as implied by a 48.37 d period. In the binarymodel, there is also a natural mechanism to explain thesteady, secular evolution of the light curve over years anddecades, namely precession of the warped circumbinarydisk.

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Figure 1: Schematic diagram from Winn et al. (2006)showing how the light curve of KH 15D is produced atone epoch in the mid-2000’s by a binary system in which arazor sharp occulting edge divides the orbits into occultedand non-occulted parts. Even when the photospheres ofboth stars are fully occulted we do see light from the sys-tem reaching us by scattering. One possibility, that thescattering arises in a halo around each star, is shown inthis figure, although other possibilities exist.

This early phase of study culminated in a comprehensivephenomenological model produced by Winn et al. (2006)that accounted for all of the photometric and radial veloc-ity data available at the time. In Fig. 1, we reproduce adiagram from that paper illustrating how the light curve isunderstood at one epoch. The secular variation with timecomes from the slow march of the occulting edge acrossthe projected orbits, driven by precession of the disk. Ex-actly how to envision this model in 3d remained a bit elu-sive, since the width of the opaque part of the occultingscreen was unknown and its location within the circumbi-nary ring (i.e. at the inner edge, outer edge, or in the mid-dle) was also unknown. Dynamical arguments by Chiang& Murray-Clay (2004) suggested that the occulting ring’scenter was near 3 AU and that it had a width of 1-2 AU.The precession time scale in their model is around 1000yrs. To precess as a single unit the disk must be warpedand there must be communication between the various an-nuli of the ring through either pressure forces from associ-ated gas or the self-gravity of ring particles. This model ofthe system, an eccentric binary situated within a warped,precessing ring, leads to the prediction that, eventually,the star causing the eclipse behavior in 2006 would itselfbe fully occulted, while the other star should reappear at

some future time and the eclipses would begin again. Howlong that might take – years, decades, centuries – was any-body’s guess in 2006.

With a basic model in hand, the next phase of study fo-cused on exploiting this very lucky geometry to learn asmuch as possible about the stars, their magnetospheres,the inner jet, and the circumbinary ring. Numerous stud-ies were launched, employing high resolution spectroscopyat Keck/HIRES, VLT/UVES, Magellan/MIKE and otherfacilities as well as continual ground-based photometricmonitoring, and episodic observations from space employ-ing HST, Spitzer and Chandra. The photometric datarevealed that the rotation period of the visible componentof the system was 9.6 d, slow for a star of this mass and age(Hamilton et al. (2005). A Chandra study showed thatthe system is also a weaker than expected X-ray source,possibly because of its slower rotation (Herbst & Moran2006). It is possible that the star’s rotation has becomepseudo-synchronized with the orbital period, as tidal the-ory in a binary system such as this would predict (Hut1981). The awesome complexity of the magnetosphere andinner jet-launching regions were probed by what we called“natural coronagraphy” – the technique of using the ra-zor sharp and highly opaque edge of the occulting ring toprogressively eliminate or reveal during each cycle vari-ous parts of the stellar surface and extended atmospheres.Results from these studies are presented in several papers,including Mundt et al. (2010) and Hamilton et al. (2012).Among other things they show that the jet is launchednot by one of the stars alone but by the combined actionof both stars, possibly during periastron passage. We alsofound evidence for enhanced accretion – “pulsed accre-tion” – that occurs during or just after periastron passageas predicted by some theories. Finally, there is spectro-scopic evidence for gas streams crossing the largely evacu-ated inner hole of the CB ring, feeding the accretion ontoone or both of the stars, again as some models, e.g. deVal-Borro et al. (2011), predict.

Studies of the ring itself have also been illuminating. Thelight and color curves can be used to infer the transparencyof the ring edge as a function of wavelength. Remark-ably, each eclipse is well modeled by a razor sharp edgewith no transparency whatsoever at optical or even near-IR wavelengths (Herbst et al. 2010). Furthermore, wecould find no evidence of a concentration of gas towardsthe ring plane in an analysis of the Na I feature (Lawleret al. 2010). Grain size estimates from polarization andscattering properties indicate that substantial growth hasoccurred (Agol et al. 2004, Herbst et al. 2008). Withoutsuch growth it would indeed be hard to understand howthe ring solids could have settled within the gaseous diskto form such a sharp-edged structure. A picture emergesof a physically thin ring of solids spanning the terrestrial

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planet formation zone around a close binary. It has longbeen thought (Goldreich & Ward 1973; Chiang & Youdin2010) that such structures are a likely first stage in the for-mation of km-sized planetesimals. It is interesting that, sofar, there is no indication of this ring in any other observedcharacteristic of KH 15D. If we were viewing this systemfrom almost any other direction in space or almost anyother time we would not know that this ring was present.If it is a first step in planetesimal formation and if plan-ets are a common feature of all stars, even binaries, thensuch rings may also be expected to be common. What wehave come to recognize about KH 15D is that its unusualproperties arise only because we see it at a very fortunatetime from a very fortunate location. It must, in fact, bea very common sort of object and, therefore, of generalimportance to star and planet formation studies.

Figure 2: The light curve of KH 15D phased with theorbital period of 48.37d. Each year of observation is codedby a different color, moving across the optical spectrumfrom red, for the earliest data in 1995, to violet and finallyblack for the most recent data plotted here, which wereobtained in 2010. This figure covers the period of evolutionduring which the occulting screen progressively coveredmore and more of the orbits. During the last two seasons,2011 and 2012, the system brightened again, as shownin Fig. 3 because the trailing edge of the screen now hasbegun to reveal the orbit of the second star.

The steady progression of the occulting edge across thebinary continued throughout the first decade of the newmillenium and by 2010 both stars were fully occulted atall orbital phases. Since neither stellar photosphere wasever seen directly, the KH 15D system brightness never gotabove 17th magnitude. The phased light curves from 1995until 2010 are shown in Fig. 2. Each year has a differentcolor code following the optical spectrum from red for theearliest data to blue for the most recent. The flat portionat around I = 14.5 mag corresponds to phases when the

non-occulted star (see Fig. 1) is fully visible. The one datapoint lying above that level was obtained in 1995, on ourthird night of observation of the system, and represented(until recently) the only detection in the modern data setof the other star. Most likely, both stars were visible at thetime of this observation. It is interesting that, even whenboth stellar photospheres are fully occulted, the systemcontinues to vary on the orbital period of 48.37 d, andby a substantial amount. The amount of scattered lightreaching us is highly modulated by the orbit. The detailsof the scattering remain uncertain. One possibility is thateach star has a scattered light halo, as depicted in Fig. 1.Other possibilities are that forward scattering from thering edge (Silvia & Agol 2008) or back scattering from thefar side of the ring (Herbst et al. 2008) are important.

A third phase of studies of this system began about ayear ago when continued photometric monitoring with theSMARTS 1.3m/ANDICAM indicated that it was bright-ening again. Coincidentally, a GeminiN/GNIRS spectrumrevealed that the spectral class of the system was nowK1, rather than K7. The change in effective temperaturewas confirmed by the V-I color, which was bluer at max-imum brightness by about 0.3 mag than it had been inthe mid-2000’s. These facts suggested that the expectedappearance of the previously fully occulted star was com-ing sooner rather than later. In March 2012 we were ableto obtain a Keck/HIRES spectrum of the system whichconfirmed that result (Capelo et al. 2012). Referring toFig. 1, we now can locate the left hand, or “trailing” edgeof the occulting ring. The width of the screen turns outto be only slightly larger than the full extent of the orbits.The system spent only two years in full occultation at allphases, even near apastron. The full light curve of thesystem from 1995 until present (Fig. 3) reveals the situ-ation. Deep eclipses have begun again, now with star Bas the eclipsed object. True to its form, though, KH 15Dcontinues to surprise us. Our expectation was that starB would be brighter than star A. The evidence is that itsspectral class, K1, indicates a hotter star than the K7 typeassigned to star A, and the fact that the system bright-ness was inferred to be more than 0.75 mag brighter in Iduring the 1960’s when both stars were visible. But themost recent data indicate the opposite ... that star B isabout 0.5 mag fainter than star A.

What does the future hold for this system? We have anamazing light curve from Spitzer/IRAC obtained duringthe YSOVAR2 project led by John Stauffer that will allowus to place better constraints on the grain size distribution,since there is some evidence of transparency at 3.6 and4.5 µm. We have a marginal detection of KH 15D at sub-millimeter wavelengths obtained with the SMA and hopeto confirm it one day with ALMA. It would be very in-teresting to know what the evolutionary state of the outer

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1995 2000 2005 2010Year

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I (m

ag)

KH 15D

Figure 3: The light curve of KH 15D from Capelo et al.(2012) including the most recent data showing its returnto a brighter state near apastron passage. The bluer color,earlier spectral class and radial velocity confirm that weare now seeing the other star in the system, the one to theleft in Fig. 1. Unexpectedly it appears to be hotter butless luminous than its companion. Relative masses havenot yet been determined.

disk is like. The system is now a double-lined eclipsingspectroscopic binary, albeit an unusual one in which theeclipses come from a circumbinary disk, not the companionstar. Nonetheless it can be utilized just like an ordinarySB2 to determine very accurate values of the fundamentalparameters of the stars including mass, radius, luminos-ity and effective temperature. An updated version of theapproach utilized by Winn et al. (2006) should constrainthese quantities, providing a nice challenge to models ofstellar evolution.

In the early days of studying this object I was often chas-tised (in good-natured fashion, of course) by my colleaguesfor devoting so much research time to a “peculiar” object.Among other things, I was told that the system could havelittle impact on planet formation theories because it wasa binary system and planet formation would be inhibited.With the recent discoveries of planets in both circumbi-nary (Doyle et al. 2011; Welsh et al. 2011; Orosz etal. 2012a,b) and circumstellar (α Cen B) orbits aroundbinary stars we now know that this is not true. It haseven been argued (Alexander 2012) that planet formationmay be enhanced in some circumbinary disks. Tatooine-like systems may be quite common in our galaxy, and KH15D, because of its fortunate alignment in space, may bea critical object for extending our understanding of planetformation in binaries and elsewhere.

I want to finish by acknowledging my many esteemed col-

leagues who have accompanied and guided me on this jour-ney of discovery particularly Catrina Hamilton, ReinhardMundt, Josh Winn, Chris Johns-Krull, Sandy Leggett andJohn Johnson. It has been a great pleasure to work withall of them. The title of this essay is courtesy of JoshWinn.

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9

Perspective

Star Formation in Atomicand Molecular Gas

Mark Krumholz

In the nearby universe, the relationship between star for-mation and molecular gas is obvious, since star-formingregions are invariably located within in molecular clouds.However, correlation does not prove causation, and thequestion of why star formation is correlated with the molec-ular phase of the interstellar medium (ISM) turns out tobe a subtle one. To begin answering it, we must first takea step back to a more basic one: why do some parts ofthe interstellar medium form stars, while other parts donot? Until roughly five years ago, the answer would haveseemed straightforward: stars form wherever galactic disksare gravitationally unstable (e.g. Quirk 1972), as indicatedby a Toomre (1964) Q parameter less than ∼ 1. This ideawas supported by Hα imaging that appeared to indicatesharp edges to the star-formation in nearby galactic disksaround the radii where Q changed from ∼ 1 to ≫ 1 (Mar-tin & Kennicutt 2001). In this view, the transition fromH i to H2 is neither sufficient nor necessary for star forma-tion. Instead, molecular clouds, as gravitationally boundobjects, are simply the markers of where the ISM is gravi-tationally unstable, and the same gravitational instabilitythat forms molecular clouds also produces stars.

However, this simple picture has encountered serious ob-servational difficulties in the past few years. First, GALEXshowed that star formation in many galactic disks doesnot in fact cease where Q ≫ 1 (Boissier et al. 2007). Sec-ond, the THINGS survey found no significant correlationbetween star formation and the value of Q on ∼ 1 kpcscales (Leroy et al. 2008). On the other hand, there isa threshold gas column density at which the ISM transi-tions from predominantly atomic to predominantly molec-ular, and star formation does diminish greatly outsidethat molecular-dominated region (Bigiel et al. 2008, 2010;Wyder et al. 2009). Moreover, the value of the thresh-old is sensitive to the metallicity of the gas (Fumagalli,

Krumholz, & Hunt 2010; Bolatto et al. 2011), and thereis no obvious reason that the Toomre Q value should besensitive to metallicity. This is strong evidence that theremust be some other factor determining where stars do anddo not form.

The observed relationship between H2 and star formationled to a number of theoretical models to calculate underwhat conditions the H i to H2 transition occurs, and touse this as a marker for where star formation will occur(Robertson & Kravtsov 2008; Krumholz, McKee, & Tum-linson 2008, 2009a, 2009b; Gnedin, Tassis, & Kravtsov2009; McKee & Krumholz 2010). In these models, metal-licity matters because H2 forms predominantly via a grain-catalyzed reaction, and because grains provide extinctionthat shields H2 molecules from the photodissociating in-terstellar radiation field (ISRF). Therefore lowering themetallicity (and thus the dust abundance) makes it harderto form H2. To first order, the models predict that theH i-H2 transition should occur at critical column density∼ 10/Z ′ M⊙ pc−1, where Z ′ is the metallicity normalizedto Solar. These models very successfully reproduce the ob-served H i to H2 transition (e.g. Lee et al. 2012) and theassociated jump in the star formation rate, and as illus-trated in Figure 1, they correctly predicted its metallicity-dependence before it was observationally measured (Bo-latto et al. 2011).

However, these models are still partly phenomenological,because they simply assume that stars form only in H2;they do not answer the question why this should be so.Schaye (2004) proposed the earliest version of an answer.He argued that the onset of gravitational instability ingalactic disks is caused by the appearance of a cold atomicphase in the ISM, which in turn is dictated primarily bythe gas surface density. This inverts the direction of causa-tion from the classical model: a temperature drop causesinstability and thus star formation, rather than instabil-ity causing the formation of dense clouds that then be-come cold. While the metallicity-dependence predictedby Schaye’s model turns out to be too weak to match theobservations shown in Figure 1 and similar data, the un-derlying idea that what triggers star formation is a loss ofthermal pressure support is a powerful one.

Krumholz, Leroy, & McKee (2011; hereafter KLM), pickedup on this idea by considering simple spherical clouds andcalculating their equilibrium temperature and chemicalstate (H i- versus H2-dominated, C+ versus CO-dominated)as a function of the clouds’ volume density and visual ex-tinction. From the temperature T and density n, they alsocalculate the clouds’ Bonnor-Ebert mass, MBE ∝ T 3/2/n.They find that, over a very wide range of cloud parame-ters, there is an excellent correlation between the presenceof large quantities of H2 and low values of MBE. KLM ar-gue that this is the reason that star formation occurs in

10

Figure 4: Observed relationship between the gas massΣgas (including both H i and H2) and star formation rateΣSFR per unit area in the Small Magellanic Cloud. Thegrayscale shows the fraction of 12 pc-sized pixels in theSMC that fall into a given box on the Σgas −ΣSFR plane.The solid black line labelled cZ = 0.2 is the prediction ofKrumholz, McKee, & Tumlinson (2009b) for the SMC’smetallicity. The dashed black line cZ = 1 is the corre-sponding prediction for Solar metallicity, and provides agood fit to the roughly solar metallicity galaxies sampledby Bigiel et al. (2008). Courtesy A. Bolatto and the AAS.

molecular gas.

The physical origin of the temperature-H2 correlation iseasy to understand. The chemical state of the gas is con-trolled by the balance between H2 formation on dust grainsand photodissociation by the interstellar radiation field.The formation rate per unit volume scales as n2Z ′, whilethe dissociation rate scales as nZ ′Ue−τ , where U is thestrength of the ISRF and τ is the dust optical depth. Sim-ilarly, the temperature is controlled by a balance betweenline cooling and heating via the grain photoelectric effect.The cooling rate scales as n2Z ′, and the heating rate asnZ ′Ue−τ , exactly as the formation and photodissociationrates. Given the nearly identical functional forms, it is notsurprising that gas that becomes molecular should also becold, and vice-versa. Moreover, it turns out that whatmatters most is shielding and not cooling, so it makeslittle difference for star formation whether the carbon ispredominantly in the form of C+ or CO. Thus one pre-dicts that, in gas where the chemical composition is suchthat the hydrogen is mostly H2 but the carbon is mostlyC+, star formation should occur. Bolatto et al. (2011) findthis to be the case in the SMC, and Schruba et al. (2012)

obtain similar results for other low-metallicity dwarfs.

Glover & Clark (2012a, hereafter GC12a) investigate asimilar question using turbulent hydrodynamic simulationsincluding time-dependent chemistry and optically-thin linecooling. In their simulations, they investigate the role ofdifferent chemical and cooling processes by turning themon and off. Due to the computational cost they are un-able to explore a wide parameter space as KLM do, buttheir approach has the significant advantage that they candirectly measure the rate of star formation in the simula-tions, rather than relying on a conjectured relationshipbetween MBE and star formation. Their numerical resultsreinforce the picture described above. They find that thestar formation rate in their simulations is essentially un-changed by whether or not they include the chemical tran-sitions from H i to H2 or C+ to CO, and the concomitantchange in available line cooling channels. However, if theydo not include dust shielding and simply assume that thegas is optically thin to the interstellar radiation field (i.e. ifthey set τ = 0 in the cooling term above), they find thatstar formation is almost entirely suppressed. The under-lying reason is that photoelectric heating keeps the gaswarm, preventing the development of cold, dense, gravi-tationally unstable structures. Figure 2 shows a sampleresult from their simulations.

The realization that the relationship between H2 and starformation is not causal, however, opens up an interest-ing possibility, again calculated analytically by Krumholz(2012) and numerically by Glover & Clark (2012b). Themodels of KLM and GC12a show that the equilibriumchemical and thermal states of interstellar gas are stronglycorrelated, such that only gas where the equilibrium chem-ical state is H2-dominated are also cold enough to formstars. However, the time required to reach thermal equi-librium is ∼ 3 orders of magnitude shorter than the timerequired to reach chemical equilibrium – formation of H2

via grain catalysis is simply a very slow process! In theMilky Way today this does not matter much, because bothprocesses are relatively fast compared to typical dynam-ical times in galaxies or even inside molecular clouds. Itmatters little if gas cools before coming to chemical equi-librium, if both processes take less time than is requiredfor the gas to undergo gravitational collapse.

However, both cooling and H2 formation rates are propor-tional to the metallicity, and thus the timescales for bothprocesses vary as Z ′−1. Since dynamical times do notscale with metallicity, this means that, at sufficiently lowmetallicity, one enters a regime where dynamical times aresmaller than chemical equilibration times, but still longerthan cooling times. By comparing equilibrium chemi-cal models to time-dependent simulations, Krumholz &Gnedin (2011) find that this regime begins at Z ′ ∼ 0.01.At such low metallicities, initially atomic clouds can cool

11

Figure 5: Distribution of gas density and temperature inthree simulations by GC12a. The top panel is a simulationwith full chemistry, but where dust shielding is ignored.The middle panel is a simulation where shielding is in-cluded, but the gas is atomic and no chemical reactionsthat convert either H or C to molecular form are allowed.The bottom panel is a simulation with full chemistry andshielding. Notice the absence of dense, cold gas in the toppanel, and its presence in the two bottom ones. CourtesyS. Glover.

and proceed to star formation before the bulk of their masscan convert to molecular form. Figure 3 shows an exam-ple calculation of the thermal and chemical evolution ofa cloud from Krumholz (2012). The important point totake from the figure is that, for the cloud shown, the timerequired for the gas to cool to near its equilibrium temper-ature is no more than a free-fall time even at metallicitiesas low as logZ ′ = −4. On the other hand, for metallicitiesbelow logZ ′ = 0.5 it does not reach 50% H2 compositionuntil more than 1 free-fall time, and for metallicities belowlogZ ′ = −1.5 it requires more than 10 free-fall times tobecome H2-dominated. It seems likely that such a cloudwould form stars and disperse by star formation feedbackbefore converting a significant fraction of its mass to H2.

The implication of this result is that, in very low metal-licity galaxies, star formation should be associated withcold atomic clouds rather than molecular ones. Checking

logZ

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-5 -4 -3 -2 -1 0 1 20.0

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Figure 6: Time evolution of gas temperature (black lines,left axis) and H2 mass fraction (blue dashed lines, rightaxis) for a cloud with density 30 cm−3, extinction AV = 2mag, initial temperature T = 1000 K, and initial compo-sition pure H i. Lines are labelled by the metallicity Z ′,from Solar to 10−4 Solar. Times are measured in free-fall times, with the gray vertical lines indicating 1 and 10free-fall times. Taken from Krumholz (2012).

this observationally will be somewhat tricky. At very lowmetallicities, CO ceases to be a reliable tracer of moleculargas (Wolfire, Hollenbach, & McKee 2010; Glover & MacLow 2011), and thus it is difficult to determine if H2 ispresent or not. However, using dust observations togetherwith high resolution 21 cm maps it is possible to estimatethe masses in the molecular and atomic phases (Bolattoet al. 2011), and thereby to check the predictions of thesemodels. ALMA observations of the dust combined withVLA 21 cm maps of very low-metallicity dwarfs seem themost promising route for a future observational test.

Bigiel, F., et al. 2008, AJ, 136, 2846

—. 2010, AJ, 140, 1194

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Gnedin, N. Y., Tassis, K., & Kravtsov, A. V. 2009, ApJ, 697, 55

Glover, S. C. O., & Clark, P. C. 2012a, MNRAS, 421, 9

—. 2012b, MNRAS, 326, 377

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Krumholz, M. R. 2012, ApJ, 759, 9

Krumholz, M. R., & Gnedin, N. Y. 2011, ApJ, 729, 36

Krumholz, M. R.., Leroy, A. K., & McKee, C. F. 2011, ApJ, 731, 25

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12

Abstracts of recently accepted papers

Protostars, multiplicity, and disk evolution in the Corona Australis region:A Herschel Gould Belt Study

Aurora Sicilia Aguilar1, Thomas Henning2, Hendrik Linz2, Philippe Andre3, Amy Stutz2, Carlos Eiroa1

and Glenn J. White4,5

1 Departamento de Fısica Teorica, Facultad de Ciencias, Universidad Autonoma de Madrid, 28049 Cantoblanco,Madrid, Spain2 Max-Planck-Institut fur Astronomie, Konigstuhl 17, 69117 Heidelberg, Germany3 Laboratoire AIM, CEA/DSM–CNRS–Universite Paris Diderot, IRFU/Service d’Astrophysique, CEA Saclay, 91191Gif-sur-Yvette, France4 RAL Space, STFC Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire, OX11 0QX, UK5 Department of Physical Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK

E-mail contact: aurora.sicilia at uam.es

The CrA region and the Coronet cluster form a nearby (138 pc), young (1-2 Myr) star-forming region hosting amoderate population of YSO. We present Herschel PACS photometry at 100 and 160 µm, obtained as part of theHerschel Gould Belt Survey. The Herschel maps reveal the cluster members with high sensitivity and high dynamicrange. Many of the cluster members are detected, including some embedded, very low-mass objects, several protostars,and substantial emission from the surrounding cloud. The Herschel data provide sufficient spatial resolution to detectsmall-scale details, such as bright filaments around the IRS5 protostar complex and a bubble-shaped rim associatedwith the Class I object IRS2. The disks around the Class II objects display a wide range of mid- and far-IR excessesconsistent with different disk structures. We have modeled the disks using the RADMC radiative transfer code,finding an interesting mixture of objects for a young and presumably coeval cluster. Some of them are consistentwith flared, massive, relatively primordial disks (SCrA, TCrA). Others display significant evidence for inside–outevolution, consistent with the presence of inner holes/gaps (G-85, G-87). Finally, we find disks with a dramatic smalldust depletion (G-1, HBC677) that, in some cases, could be related to truncation or to the presence of large gapsin a flared disk (CrA-159). The derived masses for the disks around the low-mass stars are found to be below thetypical values in Taurus, in agreement with previous Spitzer observations. Given the high degree of multiplicity andinteractions observed among the protostars in the region, the diversity of disks may be a consequence of the earlystar formation history, which should also be taken into account when studying the disk properties in similar sparselypopulated clusters.

Accepted by A&A

http://arxiv.org/pdf/1211.6945

A high-resolution spectropolarimetric survey of Herbig Ae/Be stars - I. Observationsand measurements

E. Alecian1,2, G.A. Wade2, C. Catala1, J.H. Grunhut2,3, J.D. Landstreet4,5, S. Bagnulo5, T. Bohm6,7,

C.P. Folsom5, S. Marsden8,9, I. Waite9

1 LESIA-Observatoire de Paris, CNRS, UPMC Univ., Univ. Paris-Diderot, 5 place Jules Janssen, F-92195 MeudonPrincipal Cedex, France2 Dept. of Physics, Royal Military College of Canada, PO Box 17000, Stn Forces, Kingston K7K 7B4, Canada3 Department of Physics, Queen’s University, Kingston, Canada4 Dept. of Physics & Astronomy, University of Western Ontario, London N6A 3K7, Canada5 Armagh Observatory, College Hill, Armagh BT61 9DG, Northern Ireland, UK6 Universite de Toulouse; UPS-OMP; IRAP; Toulouse, France7 CNRS; IRAP; 14, avenue Edouard Belin, F-31400 Toulouse, France

13

8 Centre for Astronomy, School of Engineering and Physical Sciences, James Cook University, Townsville, 4811,Australia9 Faculty of Sciences, University of Southern Queensland, Toowoomba, 4350, Australia

E-mail contact: evelyne.alecian at obspm.fr

This is the first in a series of papers in which we describe and report the analysis of a large survey of Herbig Ae/Bestars in circular spectropolarimetry. Using the ESPaDOnS and Narval high-resolution spectropolarimeters at theCanada-France-Hawaii and Bernard Lyot Telescopes, respectively, we have acquired 132 circularly-polarised spectraof 70 Herbig Ae/Be stars and Herbig candidates. The large majority of these spectra are characterised by a resolvingpower of about 65,000, and a spectral coverage from about 3700 ang to 1 micron. The peak SNR per CCD pixel rangesfrom below 100 (for the faintest targets) to over 1000 (for the brightest). The observations were acquired with theprimary aim of searching for magnetic fields in these objects. However, our spectra are suitable for a variety of otherimportant measurements, including rotational properties, variability, binarity, chemical abundances, circumstellarenvironment conditions and structure, etc. In this first paper, we describe the sample selection, the observations andtheir reduction, and the measurements that will comprise the basis of much of our following analysis. We describe thedetermination of fundamental parameters for each target. We detail the Least-Squares Deconvolution that we haveapplied to each of our spectra, including the selection, editing and tuning of the LSD line masks. We describe thefitting of the LSD Stokes I profiles using a multi-component model that yields the rotationally-broadened photosphericprofile (providing the projected rotational velocity and radial velocity for each observation) as well as circumstellaremission and absorption components. Finally, we diagnose the longitudinal Zeeman effect via the measured circularpolarisation, and report the longitudinal magnetic field and Stokes V Zeeman signature detection probability. As anappendix, we provide a detailed review of each star observed.

Accepted for publication in MNRAS

http://arxiv.org/pdf/1211.2907

A high-resolution spectropolarimetric survey of Herbig Ae/Be stars - II. Rotation

E. Alecian1,2, G.A. Wade2, C. Catala1, J.H. Grunhut2,3, J.D. Landstreet4,5, T. Bohm6,7, C.P. Folsom5,

S. Marsden8,9

1 LESIA-Observatoire de Paris, CNRS, UPMC Univ., Univ. Paris-Diderot, 5 place Jules Janssen, F-92195 MeudonPrincipal Cedex, France2 Dept. of Physics, Royal Military College of Canada, PO Box 17000, Stn Forces, Kingston K7K 7B4, Canada3 Department of Physics, Queen’s University, Kingston, Canada4 Dept. of Physics & Astronomy, University of Western Ontario, London N6A 3K7, Canada5 Armagh Observatory, College Hill, Armagh BT61 9DG, Northern Ireland, UK6 Universite de Toulouse; UPS-OMP; IRAP; Toulouse, France7 CNRS; IRAP; 14, avenue Edouard Belin, F-31400 Toulouse, France8 Centre for Astronomy, School of Engineering and Physical Sciences, James Cook University, Townsville, 4811,Australia9 Faculty of Sciences, University of Southern Queensland, Toowoomba, 4350, Australia

E-mail contact: evelyne.alecian at obspm.fr

We report the analysis of the rotational properties of our sample of Herbig Ae/Be (HAeBe) and related stars for whichwe have obtained high-resolution spectropolarimetric observations. Using the projected rotational velocities measuredat the surface of the stars, we have calculated the angular momentum of the sample and plotted it as a function ofage. We have then compared the angular momentum and the v sin i distributions of the magnetic to the non-magneticHAeBe stars. Finally we have predicted the v sin i of the non-magnetic, non-binary (”normal”) stars in our samplewhen they reach the ZAMS, and compared them to various catalogues of the v sin i of main-sequence stars. First,we observe that magnetic HAeBe stars are much slower rotators than normal stars, indicating that they have beenmore efficiently braked than the normal stars. In fact, the magnetic stars have already lost most of their angularmomentum, despite their young ages (lower than 1 Myr for some of them). Secondly, our analysis suggests that thelow mass (1.5 < M < 5 M⊙) normal HAeBe stars evolve with constant angular momentum towards the ZAMS, whilethe high-mass normal HAeBe stars (M > 5 M⊙) are losing angular momentum. We propose that winds, which areexpected to be stronger in massive stars, are at the origin of this phenomenon.

14

Accepted by MNRAS

http://arxiv.org/pdf/1211.2911

Spectroscopy of brown dwarf candidates in IC 348 and the determination of its substellarIMF down to planetary masses

C. Alves de Oliveira1, E. Moraux2, J. Bouvier2, G. Duchene2,3, H. Bouy4, T. Maschberger2, and P.

Hudelot5

1 European Space Astronomy Centre (ESA), P.O. Box 78, 28691 Villanueva de la Canada, Madrid, Spain2 UJF-Grenoble 1/CNRS-INSU, Institut de Planetologie et d’Astrophysique de Grenoble (IPAG) UMR5274, Grenoble,38041, France3 Astronomy Department, University of California, Berkeley, CA 947203411, USA4 Centro de Astrobiologa (INTA-CSIC); LAEFF, P.O. Box 78, 28691 Villanueva de la Canada, Spain5 Institut d’Astrophysique de Paris, UMR 7095 CNRS, Universite Pierre et Marie Curie, 98bis Bd Arago, 75014 Paris,France

E-mail contact: calves at sciops.esa.int

Context. Brown dwarfs represent a sizable fraction of the stellar content of our Galaxy and populate the transitionbetween the stellar and planetary mass regime. There is however no agreement on the processes responsible for theirformation.Aims. We have conducted a large survey of the young, nearby cluster IC 348, to uncover its low-mass brown dwarfpopulation and study the cluster properties in the substellar regime.Methods. Deep optical and near-IR images taken with MegaCam andWIRCam at the Canada-France-Hawaii Telescope(CFHT) were used to select photometric candidate members. A spectroscopic follow-up of a large fraction of thecandidates was conducted to assess their youth and membership.Results. We confirmed spectroscopically 16 new members of the IC 348 cluster, including 13 brown dwarfs, contributingsignificantly to the substellar census of the cluster, where only 30 brown dwarfs were previously known. Five of thenew members have a L0 spectral type, the latest-type objects found to date in this cluster. At 3 Myr, evolutionarymodels estimate these brown dwarfs to have a mass of ∼13 Jupiter masses. Combining the new members with previouscensus of the cluster, we constructed the IMF complete down to 13 Jupiter masses.Conclusions. The IMF of IC 348 is well fitted by a log-normal function, and we do not see evidence for variations ofthe mass function down to planetary masses when compared to other young clusters.

Accepted by A&A

http://arxiv.org/pdf/1211.4029

The mid-infrared extinction law in the darkest cores of the Pipe Nebula

J. Ascenso1, C. J. Lada2, J. Alves3, C. G. Roman-Zuniga4, and M. Lombardi5

1 European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching bei Munchen, Germany2 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA3 University of Vienna, Turkenschanzstrasse 17, 1180 Vienna, Austria4 Instituto de Astronomıa, Unidad Academica de Ensenada, Universidad Autonoma de Mexico. Ensenada 22860Mexico5 University of Milan, Department of Physics, via Celoria 16, 20133 Milan, Italy

Context. The properties of dust grains, in particular their size distribution, are expected to differ from the interstellarmedium to the high-density regions within molecular clouds.Aims. We measure the mid-infrared extinction law produced by dense material in molecular cloud cores. Since theextinction at these wavelengths is caused by dust, the extinction law in cores should depart from that found in low-density environments if the dust grains have different properties.Methods. We use the unbiased LINES method to measure the slope of the reddening vectors in color-color diagrams.We derive the mid-infrared extinction law toward the dense cores B59 and FeSt 1-457 in the Pipe Nebula over a rangeof visual extinction between 10 and 50 magnitudes, using a combination of Spitzer/IRAC, and ESO NTT/VLT data.

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Results. The mid-infrared extinction law in both cores departs significantly from a power-law between 3.6 and 8micron, suggesting that these cores contain dust with a considerable fraction of large dust grains. We find no evidencefor a dependence of the extinction law with column density up to 50 magnitudes of visual extinction in these cores, andno evidence for a variation between our result and those for other clouds at lower column densities reported elsewherein the literature. This suggests that either large grains are present even in low column density regions, or that theexisting dust models need to be revised at mid-infrared wavelengths. We find a small but significant difference in theextinction law of the two cores, that we tentatively associate with the onset of star formation in B59.

Accepted to A&A

http://arxiv.org/pdf/1211.6556

Bayesian inference of T Tauri star properties using multi-wavelength survey photometry

Geert Barentsen1,2, Jorick S. Vink1, Janet E. Drew2, and Stuart E. Sale3

1 Armagh Observatory, College Hill, Armagh BT61 9DG, U.K.2 Centre for Astrophysics Research, Science and Technology Research Institute, University of Hertfordshire, HatfieldAL10 9AB, U.K.3 Rudolf Peierls Centre for Theoretical Physics, Keble Road, Oxford OX1 3NP, U.K.

E-mail contact: geert at barentsen.be

There are many pertinent open issues in the area of star and planet formation. Large statistical samples of youngstars across star-forming regions are needed to trigger a breakthrough in our understanding, but most optical studiesare based on a wide variety of spectrographs and analysis methods, which introduces large biases. Here we show howgraphical Bayesian networks can be employed to construct a hierarchical probabilistic model which allows pre-mainsequence ages, masses, accretion rates, and extinctions to be estimated using two widely available photometric surveydatabases (IPHAS r/i/Hα and 2MASS J-band magnitudes.) Because our approach does not rely on spectroscopy, itcan easily be applied to homogeneously study the large number of clusters for which Gaia will yield membership lists.We explain how the analysis is carried out using the Markov Chain Monte Carlo (MCMC) method and provide Pythonsource code. We then demonstrate its use on 587 known low-mass members of the star-forming region NGC 2264 (ConeNebula), arriving at a median age of 3.0 Myr, an accretion fraction of 20±2% and a median accretion rate of 10−8.4

M⊙ yr−1. The Bayesian analysis formulated in this work delivers results which are in agreement with spectroscopicstudies already in the literature, but achieves this with great efficiency by depending only on photometry. It is asignificant step forward from previous photometric studies, because the probabilistic approach ensures that nuisanceparameters, such as extinction and distance, are fully included in the analysis with a clear picture on any degeneracies.

Accepted by MNRAS

http://arxiv.org/pdf/1211.6108

The Magnetic Topology of the Weak-Lined T Tauri Star V410 - A Simultaneous Tem-perature and Magnetic Field Inversion

T. A. Carroll1, K. G. Strassmeier1, J. B. Rice2, and A. Kuenstler1

1 Leibniz-Institute for Astrophysics Potsdam, An der Sternwarte 16, D-14482 Potsdam, Germany2 Department of Physics, Brandon University, Brandon, Manitoba R7A 6A9, Canada

E-mail contact: tcarroll at aip.de

We present a detailed temperature and magnetic investigation of the T Tauri star V410 Tau by means of a simultaneousDoppler- and Zeeman-Doppler Imaging. Moreover we introduce a new line profile reconstruction method based on asingular value decomposition (SVD) to extract the weak polarized line profiles. One of the key features of the lineprofile reconstruction is that the SVD line profiles are amenable to radiative transfer modeling within our Zeeman-Doppler Imaging code iMap. The code also utilizes a new iterative regularization scheme which is independent of anyadditional surface constraints. To provide more stability a vital part of our inversion strategy is the inversion of bothStokes I and Stokes V profiles to simultaneously reconstruct the temperature and magnetic field surface distributionof V410 Tau. A new image-shear analysis is also implemented to allow the search for image and line profile distortionsinduced by a differential rotation of the star. The magnetic field structure we obtain for V410 Tau shows a good

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spatial correlation with the surface temperature and is dominated by a strong field within the cool polar spot. TheZeeman-Doppler maps exhibit a large-scale organization of both polarities around the polar cap in the form of atwisted bipolar structure. The magnetic field reaches a value of almost 2 kG within the polar region but smaller fieldsare also present down to lower latitudes. The pronounced non-axisymmetric field structure and the non-detectionof a differential rotation for V410 Tau supports the idea of an underlying α2-type dynamo, which is predicted forweak-lined T Tauri stars.

Accepted by A&A

http://arxiv.org/pdf/1211.2720

A close-up view of a bipolar jet: Sub-arcsecond near-IR imaging of the high-mass pro-tostar IRAS20126+4104

R. Cesaroni1, F. Massi1, C. Arcidiacono1,2, M.T. Beltran1, D. McCarthy3, C. Kulesa3, K. Boutsia4, D.

Paris4, F. Quiros-Pacheco1 and M. Xompero1

1 INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125 Firenze, Italy2 INAF, Osservatorio Astronomico di Bologna, Via Ranzani 1, I-40127 Bologna, Italy3 Steward Observatory, The University of Arizona, 933 N. Cherry Ave., Tucson, AZ-85721, USA4 INAF, Osservatorio Astronomico di Roma, via Frascati 33, I-00040, Monteporzio, Italy

E-mail contact: cesa at arcetri.astro.it

The formation of OB-type stars up to (at least) 140 M⊙ can be explained via disk-mediated accretion and in factgrowing observational evidence of disk-jet systems is found in high-mass star-forming regions. With the presentobservations we wish to investigate at sub-arcsecond resolution the jet structure close to the well studied high-massprotostar IRAS 20126+4104, which is known to be surrounded by a Keplerian disk. Adaptive optics imaging of the2.2 µm continuum and H2 and Brγ line emission have been performed with the Large Binocular Telescope, attainingan angular resolution of ∼90 mas and an astrometric precision of ∼100 mas. While our results are consistent withprevious K-band images by other authors, the improved (by a factor ∼3) resolution allows us to identify a numberof previously unseen features, such as bow shocks spread all over the jet structure. Also, we confirm the existenceof a bipolar nebulosity within 1′′ from the protostar, prove that the emission from the brightest, SE lobe is mostlydue to the H2 line, and resolve its structure. Comparison with other tracers such as masers, thermal molecular lineemission, and free-free continuum emission proves that the bipolar nebulosity is indeed tracing the root of the bipolarjet powered by the deeply embedded protostar at the center of the Keplerian disk.

Accepted by Astronomy and Astrophysics

http://www.arcetri.astro.it/science/starform/preprints/cesa_23.pdf

The Herschel DIGIT Survey of Weak-line T Tauri Stars: implications for disk evolutionand dissipation

Lucas A. Cieza1, Johan Olofsson2, Paul M. Harvey3, Neal J. Evans II3, Joan Najita4, Thomas Henning2,

Bruno Merın5, Armin Liebhart6, Manuel Gudel6, Jean-Charles Augereau7, and Christophe Pinte7

1 Institute for Astronomy, University of Hawaii at Manoa, Honolulu, HI 96822. USA2 Max Planck Institute fur Astronomie, Konigstuhl 17, Heidelberg, Germany3 Department of Astronomy, University of Texas at Austin, 2515 Speedway, Stop C1400, Austin, TX 78712-1205, USA4 National Optical Astronomy Observatory, 950 N. Cherry Avenue, Tucson, AZ 86719, USA5 Herschel Science Centre, European Space Astronomy Centre, ESA, P.O. Box 78, 28691 Villanueva de la Canada,Madrid, Spain6 Department of Astronomy, Univ. of Vienna, Turkenschanzstr. 17, A-1180 Vienna, Austria7 UJF-Grenoble 1/CNRS-INSU, Institut de Planetologie et d’Astrophysique (IPAG) UMR 5274, BP 53, 38041 Grenoblecedex 9, France

E-mail contact: lcieza at ifa.hawaii.edu

As part of the ”Dust, Ice, and Gas In Time (DIGIT)” Herschel Open Time Key Program, we present Herschelphotometry (at 70, 160, 250, 350 and 500 micron) of 31 Weak-Line T Tauri star (WTTS) candidates in order toinvestigate the evolutionary status of their circumstellar disks. Thirteen stars in our sample had circumstellar disks

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previously known from infrared observations at shorter wavelengths, while eighteen of them had no previous evidencefor a disk. We detect a total of 15 disks as all previously known disks are detected at one or more Herschel wavelengthsand two additional disks are identified for the first time. The spectral energy distributions (SEDs) of our targets seemto trace the dissipation of the primordial disk and the transition to the debris disk regime. Seven of the 15 disksappear to be optically thick primordial disks, including two objects with SEDs indistinguishable from those of typicalClassical T Tauri stars, four objects that have significant deficit of excess emission at all IR wavelengths, and one”pre-transitional” object with a known gap in the disk. Despite their previous WTTS classification, we find that theseven targets in our sample with optically thick disks show evidence for accretion. The remaining eight disks haveweaker IR excesses similar to those of optically thin debris disks. Six of them are warm and show significant 24 micronSpitzer excesses, while the last two are newly identified cold debris-like disks with photospheric 24 micron fluxes,but significant excess emission at longer wavelengths. The Herschel photometry also places strong constraints on thenon-detections, where systems with F70/F70⋆ > 5 – 15 and Ldisk/L⋆ > 10−3 to 10−4 can be ruled out. We presentpreliminary models for both the optically thick and optically thin disks and discuss our results in the context of theevolution and dissipation of circumstellar disks.

Accepted by ApJ

http://arxiv.org/pdf/1211.4510

SiO collimated outflows driven by high-mass YSOs in G24.78+0.08

C. Codella1,2, M.T. Beltran1, R. Cesaroni1, L. Moscadelli1, R. Neri3, M. Vasta1, Q. Zhang4

1 INAF, Osservatorio Astrofisico di Arcetri, Firenze, Italy2 UJF-Grenoble 1 / CNRS-INSU, Institut de Planetologie et d’Astrophysique de Grenoble (IPAG), France3 IRAM, 300 rue de la Piscine, 38406 Saint Martin d’Heres, France4 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge MA 02138, USA

E-mail contact: codella at arcetri.astro.it

Context: The region G24.78+0.08, which is associated with a cluster of high-mass young stellar objects in differentevolutionary stages, is one of the best laboratories to investigate massive star-formation.Aims: We aim to image the molecular outflows towards G24.78+0.08 at high-angular resolution using SiO emission,which is considered the classical tracer of protostellar jets. In this way we study the mass loss process in which wepreviously detected a hypercompact ionised region, as well as rotation and infall signatures.Methods: We performed SiO observations with the VLA interferometer in the J = 1–0 v=0 transition and with theSMA array in the 5–4 transition. A complementary IRAM 30-m single-dish survey in the (2–1), (3–2), (5–4), and(6–5) SiO lines was also carried out.Results: Two collimated SiO high-velocity (up to 25 km s−1 w.r.t. the systemic velocity) outflows driven by theA2 and C millimeter continuum massive cores have been imaged. On the other hand, we detected no SiO outflowdriven by the young stellar objects in more evolved evolutionary phases that are associated with ultracompact (B) orhypercompact (A1) Hii regions. The A2 outflow has also been traced using H2S. The LVG analysis of the SiO emissionreveals high-density gas (103–104 cm−3), with well constrained SiO column densities (0.5–1 1015 cm−2). The drivingsource of the A2 outflow is associated with typical hot core tracers such as CH3OCHO (methyl formate), C2H3CN(vinyl cyanide), HCC13CN (cyanoacetilene), and (CH3)2CO (acetone).Conclusions: The driving source of the main SiO outflow in G24 has an estimated luminosity of a few 104 L⊙ (typicalof a late O-type star) and is embedded in the 1.3 mm continuum core A2, which in turn is located at the centre of ahot core that rotates on a plane perpendicular to the outflow main axis. The present SiO images support a scenariosimilar to the low-mass case for massive star formation, where jets that are clearly traced by SiO emission, createoutflows of swept-up ambient gas usually traced by CO.

Accepted by A&A

http://arxiv.org/pdf/1212.0473

A Search for Giant Planet Companions to T Tauri Stars

Christopher J. Crockett1,3, Naved I. Mahmud3,4, L. Prato2,3, Christopher M. Johns-Krull3,4, Daniel T.

Jaffe5, Patrick M. Hartigan4, Charles A. Beichman6,7

1 U.S. Naval Observatory, 10391 W. Naval Observatory Road, Flagstaff, AZ 86001, USA

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2 Lowell Observatory, 1400 W Mars Hill Road, Flagstaff, AZ 86001, USA3 Visiting Astronomer at the Infrared Telescope Facility4 Department of Physics and Astronomy, Rice University, MS-108, 6100 Main Street, Houston, TX 77005, USA5 Department of Astronomy, University of Texas, R.L. Moore Hall, Austin, TX 78712, USA6 Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA7 NASA Exoplanet Science Institute (NExScI), California Institute of Technology, 770 S. Wilson Ave, Pasadena, CA91125, USA

E-mail contact: ccrockett at nofs.navy.mil

We present results from an ongoing multiwavelength radial velocity (RV) survey of the Taurus-Auriga star formingregion as part of our effort to identify pre–main sequence giant planet hosts. These 1-3 Myr old T Tauri stars presentsignificant challenges to traditional RV surveys. The presence of strong magnetic fields gives rise to large, cool starspots. These spots introduce significant RV jitter which can mimic the velocity modulation from a planet-masscompanion. To distinguish between spot-induced and planet-induced RV modulation, we conduct observations at∼6700 A and ∼2.3 µm and measure the wavelength dependence (if any) in the RV amplitude. CSHELL observationsof the known exoplanet host Gl 86 demonstrate our ability to detect not only hot Jupiters in the near infrared butalso secular trends from more distant companions. Observations of nine very young stars reveal a typical reductionin RV amplitude at the longer wavelengths by a factor of ∼2–3. While we can not confirm the presence of planets inthis sample, three targets show different periodicities in the two wavelength regions. This suggests different physicalmechanisms underlying the optical and K band variability.

Accepted to ApJ

http://arxiv.org/pdf/1211.1389

The Young Open Clusters King 12, NGC 7788, and NGC 7790: Pre-Main SequenceStars and Extended Stellar Haloss

T. J. Davidge1

1 Dominion Astrophysical Observatory, National Research Council of Canada, 5071 West Saanich Road, Victoria, BCCanada V9E 2E7

The stellar contents of the open clusters King 12, NGC 7788, and NGC 7790 are investigated using MegaCam images.Comparisons with isochrones yield an age < 20 Myr for King 12, 20–40 Myr for NGC 7788, and 60 – 80 Myr forNGC 7790 based on the properties of stars near the main sequence turn-off (MSTO) in each cluster. The reddening ofNGC 7788 is much larger than previously estimated. The luminosity functions (LFs) of King 12 and NGC 7788 showbreaks that are attributed to the onset of pre-main sequence (PMS) objects, and comparisons with models of PMSevolution yield ages that are consistent with those measured from stars near the MSTO. In contrast, the r’ LF of mainsequence stars in NGC 7790 is matched to r’ = 20 by a model that is based on the solar neighborhood mass function.The structural properties of all three clusters are investigated by examining the two-point angular correlation functionof blue main sequence stars. King 12 and NGC 7788 are each surrounded by a stellar halo that extends out to 5arcmin (∼ 3.4 parsecs) radius. It is suggested that these halos form in response to large-scale mass ejection early inthe evolution of the clusters, as predicted by models. In contrast, blue main sequence stars in NGC 7790 are tracedout to a radius of ∼ 7.5′, with no evidence of a halo. It is suggested that all three clusters may have originated in thesame star-forming complex, but not in the same giant molecular cloud.

Accepted by Astrophysical Journal

http://arxiv.org/pdf/1211.6398

New Brown Dwarf Disks in Upper Scorpius Observed with WISE

P. Dawson1, A. Scholz1, T.P. Ray1, K.A. Marsh2, K. Wood3, A. Natta1,4, D. Padgett5 and M.E. Ressler6

1 School of Cosmic Physics, Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2, Ireland2 School of Physics and Astronomy, Cardiff University, Cardiff CF24 3AA, UK3 School of Physics and Astronomy, University of St. Andrews, North Haugh, St.Andrews KY16 9SS, UK4 INAF - Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy5 Goddard Space Flight Center, Greenbelt, MD 20771, USA

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6 Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA

E-mail contact: pdawson at cp.dias.ie

We present a census of the disk population for UKIDSS selected brown dwarfs in the 5-10 Myr old Upper Scorpius OBassociation. For 116 objects originally identified in UKIDSS, the majority of them not studied in previous publications,we obtain photometry from the WISE database. The resulting colour-magnitude and colour-colour plots clearly showtwo separate populations of objects, interpreted as brown dwarfs with disks (class II) and without disks (class III). Weidentify 27 class II brown dwarfs, 14 of them not previously known. This disk fraction (27 out of 116 or 23%) amongbrown dwarfs was found to be similar to results for K/M stars in Upper Scorpius, suggesting that the lifetimes ofdisks are independent of the mass of the central object for low-mass stars and brown dwarfs. 5 out of 27 disks (19%)lack excess at 3.4 and 4.6µm and are potential transition disks (i.e. are in transition from class II to class III). Thetransition disk fraction is comparable to low-mass stars. We estimate that the timescale for a typical transition fromclass II to class III is less than 0.4Myr for brown dwarfs. These results suggest that the evolution of brown dwarfdisks mirrors the behaviour of disks around low-mass stars, with disk lifetimes on the order of 5-10Myr and a diskclearing timescale significantly shorter than 1Myr.

Accepted by MNRAS

http://arxiv.org/pdf/1211.4484

CFBDSIR2149-0403: a 4-7 Jupiter-mass free-floating planet in the young moving groupAB Doradus ?

P. Delorme 1, J. Gagne 2, L. Malo 2, C. Reyle 3 , E. Artigau 2, L. Albert 2, T. Forveille 1, X. Delfosse1, F. Allard 4, D. Homeier 4

1UJF-Grenoble 1 / CNRS-INSU, Institut de Planetologie et d’Astrophysique de Grenoble (IPAG) UMR 5274, Greno-ble, F-38041, France.2Departement de physique and Observatoire du Mont Megantic, Universite de Montreal, C.P. 6128, Succursale Centre-Ville, Montreal, QC H3C 3J7, Canada3 Universite de Franche Comte, Institut UTINAM CNRS 6213, Observatoire des Sciences de l’Univers THETA deFranche-Comte, Observatoire de Besancon, BP 1615, 25010 Besancon Cedex, France4C.R.A.L. (UMR 5574 CNRS), Ecole Normale Superieure, 69364 Lyon Cedex 07, France

E-mail contact: philippe.delorme at obs.ujf-grenoble.fr

Using the CFBDSIR wide field survey for brown dwarfs, we identified CFBDSIRJ214947.2-040308.9, a late T dwarfwith atypically red J −KS colour. We obtained an X-Shooter spectra, with signal detectable from 0.8 µm to 2.3 µm,which confirmed a T7 spectral type with an enhanced Ks-band flux indicative of a potentially low-gravity, young,object. The comparison of our near infrared spectrum with atmosphere models, for solar metallicity, shows thatCFBDSIRJ214947.2-040308.9 is probably a 650-750K, log g=3.75-4.0 substellar object. Using evolution models, thistranslates into a planetary mass object, with an age in the 20-200 Myr range. An independent Bayesian analysis fromproper motion measurements results in a 87% probability that this free-floating planet is a member of the 50-120 Myrold AB Doradus moving group, which strengthens the spectroscopic youth diagnosis. By combining our atmosphericcharacterisation with the age and metallicity constraints arising from the probable membership to the AB Doradusmoving group, we find that CFBDSIRJ214947.2-040308.9 is probably a 4-7 Jupiter masses free-floating planet with aneffective temperature of ∼700K and a log g of ∼4.0, typical of the late T-type exoplanets that are targeted by directimaging. We stress that this object could be used as a benchmark for understanding the physics of the similar T-typeexoplanets that will be discovered by the upcoming high contrast imagers.

Accepted by A&A (548:A26)

http://arxiv.org/pdf/1210.0305

Multi-wavelength study of triggered star formation around mid-infrared bubble N14

L. K. Dewangan1,2 and D. K. Ojha1

1 Department of Astronomy and Astrophysics, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai400 005, India2 Centro de Astrofısica da Universidade do Porto, Rua das Estrelas, 4150-762 s/n Porto, Portugal

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E-mail contact: Lokesh.Dewangan at astro.up.pt

We present multi-wavelength analysis around mid-infrared (MIR) bubble N14 to probe the signature of triggeredstar formation as well as the formation of new massive star(s) and/or cluster(s) on the borders of the bubble by theexpansion of the H ii region. Spitzer-IRAC ratio maps reveal that the bubble is traced by the polycyclic aromatichydrocarbon (PAH) emission following an almost circular morphology except in the south-west direction towards thelow molecular density environment. The observational signatures of the collected molecular and cold dust materialhave been found around the bubble. We have detected 418 young stellar objects (YSOs) in the selected region aroundthe bubble N14. Interestingly, the detected YSO clusters are associated with the collected molecular and cold dustmaterial on the borders of the bubble. One of the clusters is found with deeply embedded intermediate mass andmassive Class I YSOs associated with one of the dense dust clumps in the east of the bubble N14. We do notfind a good agreement between the dynamical age of the H ii region and the fragmentation time of the accumulatedmolecular materials to explain possible “collect-and-collapse” process around the bubble N14. Therefore, we suggestthe possibility of triggered star formation by compression of the pre-existing dense clumps by the shock wave and/orsmall scale Jeans gravitational instabilities in the collected materials. We have also investigated 5 young massiveembedded protostars (8 to 10 M⊙) and 15 intermediate mass (3 to 7 M⊙) Class I YSOs which are associated withthe dust and molecular fragmented clumps at the borders of the bubble. We conclude that the expansion of the H ii

region is also leading to the formation of these intermediate and massive Class I YSOs around the bubble N14.

Accepted by the MNRAS

http://arxiv.org/pdf/1211.4079

Tracing High-Energy Radiation from T Tauri Stars Using Mid-Infrared Neon Emissionfrom Disks

C. Espaillat1,2, L. Ingleby3, E. Furlan4,5, M. McClure3, A. Spatzier6, J. Nieusma3, N. Calvet3, E.

Bergin3, L. Hartmann3, J. M. Miller3 and J. Muzerolle7

1 Sagan Fellow2 Harvard-Smithonian Center for Astrophysics, 60 Garden Street, MS-78, Cambridge, MA, 02138, USA3 Department of Astronomy, University of Michigan, 830 Dennison Building, 500 Church Street, Ann Arbor, MI 48109,USA4 National Optical Astronomy Observatory, 950 N. Cherry Ave., Tucson, AZ, 85719, USA5 Visitor at the Infrared Processing and Analysis Center, Caltech, 770 S. Wilson Ave., Pasadena, CA, 91125, USA6 Oberlin College, Wright Laboratory of Physics, 110 N. Professor St., Oberlin, OH, 44074, USA7 Space Telescope Institute, 3700 San Martin Drive, Baltimore, MD, 21218, USA

E-mail contact: cespaillat at cfa.harvard.edu

High-energy radiation from T Tauri stars (TTS) influences the amount and longevity of gas in disks, thereby playinga crucial role in the creation of gas giant planets. Here we probe the high-energy ionizing radiation from TTS usinghigh-resolution mid-infrared (MIR) Spitzer IRS Neon forbidden line detections in a sample of disks from IC 348,NGC 2068, and Chamaeleon. We report three new detections of [Ne III] from CS Cha, SZ Cha, and T 54, doublingthe known number of [Ne III] detections from TTS. Using [Ne III]-to-[Ne II] ratios in conjunction with X-ray emissionmeasurements, we probe high-energy radiation from TTS. The majority of previously inferred [Ne III]/[Ne II] ratiosbased on [Ne III] line upper limits are significantly less than 1, pointing to the dominance of either X-ray radiationor soft Extreme-Ultraviolet (EUV) radiation in producing these lines. Here we report the first observational evidencefor hard EUV dominated Ne forbidden line production in a T Tauri disk: [Ne III]/[Ne II]∼1 in SZ Cha. Our resultsprovide a unique insight into the EUV emission from TTS, by suggesting that EUV radiation may dominate thecreation of Ne forbidden lines, albeit in a minority of cases.

Accepted by ApJ

http://arxiv.org/pdf/1211.2335

The Star Formation Rate of Turbulent Magnetized Clouds: Comparing Theory, Simu-lations, and Observations

Christoph Federrath1 and Ralf S. Klessen2

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1 Monash Centre for Astrophysics, School of Mathematical Sciences, Monash University, Vic 3800, Australia2 Universitat Heidelberg, Zentrum fur Astronomie, Institut fur Theoretische Astrophysik, Albert-Ueberle-Str. 2, 69120Heidelberg, Germany

E-mail contact: christoph.federrath at monash.edu

The role of turbulence and magnetic fields is studied for star formation in molecular clouds. We derive and compare sixtheoretical models for the star formation rate (SFR)—the Krumholz & McKee (KM), Padoan & Nordlund (PN), andHennebelle & Chabrier (HC) models, and three multi-freefall versions of these, suggested by HC—all based on integralsover the log-normal distribution of turbulent gas. We extend all theories to include magnetic fields, and show that theSFR depends on four basic parameters: (1) virial parameter αvir; (2) sonic Mach number M; (3) turbulent forcingparameter b, which is a measure for the fraction of energy driven in compressive modes; and (4) plasma β = 2M2

A/M2

with the Alfven Mach number MA. We compare all six theories with MHD simulations, covering cloud masses of300 to 4 × 106M⊙ and Mach numbers M = 3–50 and MA = 1–∞, with solenoidal (b = 1/3), mixed (b = 0.4) andcompressive turbulent (b = 1) forcings. We find that the SFR increases by a factor of four between M = 5 and 50for compressive turbulent forcing and αvir ∼ 1. Comparing forcing parameters, we see that the SFR is more than10× higher with compressive than solenoidal forcing for M = 10 simulations. The SFR and fragmentation are bothreduced by a factor of two in strongly magnetized, trans-Alfvenic turbulence compared to hydrodynamic turbulence.All simulations are fit simultaneously by the multi-freefall KM and multi-freefall PN theories within a factor of twoover two orders of magnitude in SFR. The simulated SFRs cover the range and correlation of SFR column densitywith gas column density observed in Galactic clouds, and agree well for star formation efficiencies SFE = 1%–10%and local efficiencies ǫ = 0.3–0.7 due to feedback. We conclude that the SFR is primarily controlled by interstellarturbulence, with a secondary effect coming from magnetic fields.

Accepted by ApJ

http://arxiv.org/pdf/1209.2856

On the Star Formation Efficiency of Turbulent Magnetized Clouds

Christoph Federrath1 and Ralf S. Klessen2

1 Monash Centre for Astrophysics, School of Mathematical Sciences, Monash University, Vic 3800, Australia2 Universitat Heidelberg, Zentrum fur Astronomie, Institut fur Theoretische Astrophysik, Albert-Ueberle-Str. 2, 69120Heidelberg, Germany

E-mail contact: christoph.federrath at monash.edu

We study the star formation efficiency (SFE) in simulations and observations of turbulent, magnetized, molecularclouds. We find that the volumetric and column density probability distributions (PDFs) of our simulations withsolenoidal, mixed, and compressive forcing of turbulence, sonic Mach numbers of 3–50, and magnetic fields in thesuper- to the trans-Alfvenic regime, all develop power-law tails of flattening slope with increasing SFE. The high-density tails of the PDFs are consistent with equivalent radial density profiles, ρ ∝ r−κ with κ ∼ 1.5–2.5, in agreementwith observations. Studying velocity–size scalings, we find that all the simulations are consistent with the observedv ∝ ℓ1/2 scaling of supersonic turbulence, and seem to approach Kolmogorov turbulence with v ∝ ℓ1/3 below the sonicscale. The velocity–size scaling is, however, largely independent of the SFE. In contrast, the density–size and columndensity–size scalings are highly sensitive to star formation. We find that the power-law slope α of the density powerspectrum, P3D(ρ, k) ∝ kα, or equivalently the ∆-variance spectrum of column density, σ2

∆(Σ, ℓ) ∝ ℓ−α, switches signfrom α < 0 for SFE ∼ 0 to α > 0 when star formation proceeds (SFE > 0). We provide a relation to compute theSFE from a measurement of α. Studying the literature, we find values ranging from α = −1.6 to +1.6 in observationscovering scales from the large-scale atomic medium, over cold molecular clouds, down to dense star-forming cores.From those α values, we infer SFEs and find good agreement with independent measurements based on young stellarobject (YSO) counts, where available. Our SFE–α relation provides an independent estimate of the SFE based on thecolumn density map of a cloud alone, without requiring a priori knowledge of star-formation activity or YSO counts.

Accepted by ApJ

http://arxiv.org/pdf/1211.6433

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AKARI/IRC 18 Micron Survey of Warm Debris Disks

Hideaki Fujiwara1, Daisuke Ishihara2, Takashi Onaka3, Satoshi Takita4, Hirokazu Kataza4, Takuya

Yamashita5, Misato Fukagawa6, Takafumi Ootsubo7, Takanori Hirao8, Keigo Enya4, Jonathan P. Marshall9,

Glenn J. White10,11, Takao Nakagawa4, and Hiroshi Murakami4

1 Subaru Telescope, National Astronomical Observatory of Japan, 650 North Aohoku Place, Hilo, HI 96720, USA2 Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan3 Department of Astronomy, School of Science, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan4 Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku,Sagamihara, Kanagawa 252-5210, Japan5 National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-0015, Japan6 Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan7 Astronomical Institute, Tohoku University, 6-3 Aramaki, Aoba-ku, Sendai, Miyagi 980-8578, Japan8 Research Institute of Science and Technology for Society, Japan Science and Technology Agency, Ks Gobancho Bldg,7, Gobancho, Chiyoda-ku, Tokyo 102-0076, Japan9 Departmento Fısica Teorica, Facultad de Ciencias, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid,Spain10 Department of Physics and Astronomy, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK11 Space Science & Technology Department, The Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX110QX, UK

E-mail contact: hideaki at naoj.org

Context. Little is known about the properties of the warm (Tdust >∼ 150 K) debris disk material located close to thecentral star, which has a more direct link to the formation of terrestrial planets than the low temperature debris dustthat has been detected to date.Aims. To discover new warm debris disk candidates that show large 18 micron excess and estimate the fraction ofstars with excess based on the AKARI/IRC Mid-Infrared All-Sky Survey data.Methods. We have searched for point sources detected in the AKARI/IRC All-Sky Survey, which show a positionalmatch with A-M dwarf stars in the Tycho-2 Spectral Type Catalogue and exhibit excess emission at 18 microncompared to that expected from the Ks magnitude in the 2MASS catalogue.Results. We find 24 warm debris candidates including 8 new candidates among A-K stars. The apparent debrisdisk frequency is estimated to be 2.8 ± 0.6%. We also find that A stars and solar-type FGK stars have differentcharacteristics of the inner component of the identified debris disk candidates — while debris disks around A starsare cooler and consistent with steady-state evolutionary model of debris disks, those around FGK stars tend to bewarmer and cannot be explained by the steady-state model.

Accepted by Astronomy & Astrophysics

http://arxiv.org/pdf/1211.6365

Herschel far-infrared observations of the Carina Nebula complex II: The embeddedyoung stellar and protostellar population

B. Gaczkowski1, T. Preibisch1, T. Ratzka1, V. Roccatagliata1, H. Ohlendorf1 and H. Zinnecker2,3

1 Universitats-Sternwarte Munchen, Ludwig-Maximilians-Universitat, Scheinerstr. 1, 81679 Munchen, Germany2 Deutsches SOFIA Institut, Universitat Stuttgart, Pfaffenwaldring 31, 70569 Stuttgart, Germany3 NASA-Ames Research Center, MS 211-3, Moffett Field, CA 94035, USA

E-mail contact: preibisch at usm.uni-muenchen.de

Context: The Carina Nebula represents one of the largest and most active star forming regions known in our Galaxy.It contains numerous very massive (M ≥ 40M⊙) stars that strongly affect the surrounding clouds by their ionizingradiation and stellar winds.Aims: Our recently obtained Herschel PACS & SPIRE far-infrared maps cover the full area (≈ 8.7 deg2) of the CarinaNebula complex and reveal the population of deeply embedded young stellar objects, most of which are not yet visiblein the mid- or near-infrared.Methods: We study the properties of the 642 objects that are independently detected as point-like sources in at least

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two of the five Herschel bands. For those objects that can be identified with apparently single Spitzer counterparts,we use radiative transfer models to derive information about the basic stellar and circumstellar parameters.Results: We find that about 75% of the Herschel -detected YSOs are Class 0 protostars. The luminosities of theHerschel -detected YSOs with SED fits are restricted to values of ≤ 5400L⊙, their masses (estimated from the radiativetransfer modeling) range from ≈ 1M⊙ to ≈ 10M⊙. Taking the observational limits into account and extrapolating theobserved number of Herschel -detected protostars over the stellar initial mass function suggest that the star formationrate of the CNC is ∼ 0.017M⊙/year. The spatial distribution of the Herschel YSO candidates is highly inhomogeneousand does not follow the distribution of cloud mass. Rather, most Herschel YSO candidates are found at the irradiatededges of clouds and pillars. The far-infrared fluxes of the famous object η Car are about a factor of two lower thanexpected from observations with the Infrared Space Observatory obtained 15 years ago; this difference may be aconsequence of dynamical changes in the circumstellar dust in the Homunculus Nebula around η Car.Conclusions: The currently ongoing star formation process forms only low-mass and intermediate-mass stars, but nomassive (M ≥ 20M⊙) stars. The characteristic spatial configuration of the YSOs provides support to the picture thatthe formation of this latest stellar generation was triggered by the advancing ionization fronts.

Accepted by Astronomy & Astrophysics

http://arxiv.org/pdf/1211.2995

High-quality preprints can be obtained fromhttp://www.usm.uni-muenchen.de/people/preibisch/publications.html

Two massive stars possibly ejected from NGC 3603 via a three-body encounter

V. V. Gvaramadze1,2, A. Y. Kniazev3,4,1, A.-N. Chene5,6, and O. Schnurr7

1 Sternberg Astronomical Institute, Lomonosov Moscow State University, Universitetskij Pr. 13, Moscow 119992,Russia2 Isaac Newton Institute of Chile, Moscow Branch, Universitetskij Pr. 13, Moscow 119992, Russia3 South African Astronomical Observatory, PO Box 9, 7935 Observatory, Cape Town, South Africa4 Southern African Large Telescope Foundation, PO Box 9, 7935 Observatory, Cape Town, South Africa5 Departamento de Fısica y Astronomıa, Universidad de Valparaso, Av. Gran Bretana 1111, Playa Ancha, Casilla5030, Chile6 Departamento de Astronomıa, Universidad de Concepcion, Casilla 160-C, Chile7 Astrophysikalisches Institut Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany

E-mail contact: vgvaram at mx.iki.rssi.ru

We report the discovery of a bow-shock-producing star in the vicinity of the young massive star cluster NGC 3603using archival data of the Spitzer Space Telescope. Follow-up optical spectroscopy of this star with Gemini-South ledto its classification as O6 V. The orientation of the bow shock and the distance to the star (based on its spectral type)suggest that the star was expelled from the cluster, while the young age of the cluster (∼2 Myr) implies that theejection was caused by a dynamical few-body encounter in the cluster’s core. The relative position on the sky of theO6 V star and a recently discovered O2 If*/WN6 star (located on the opposite side of NGC 3603) allows us to proposethat both objects were ejected from the cluster via the same dynamical event – a three-body encounter between asingle (O6 V) star and a massive binary (now the O2 If*/WN6 star). If our proposal is correct, then one can ”weigh”the O2 If*/WN6 star using the conservation of the linear momentum. Given a mass of the O6 V star of 30 M⊙, wefound that at the moment of ejection the mass of the O2 If*/WN6 star was 175 M⊙. Moreover, the observed X-rayluminosity of the O2 If*/WN6 star (typical of a single star) suggests that the components of this originally binarysystem have merged (e.g., because of encounter hardening).

Accepted by MNRAS Letters

http://arxiv.org/pdf/1211.5926

Chemical and Physical Conditions in Molecular Cloud Core DC 000.4-19.5 (SL42) inCorona Australis

E. Hardegree-Ullman1, J. Harju2,3, M. Juvela3, O. Sipila3, D. C. B. Whittet1 and S. Hotzel4,5

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1 New York Center for Astrobiology and Department of Physics, Applied Physics, and Astronomy, Rensselaer Poly-technic Institute, 110 Eighth Street, Troy, NY 12180, USA2 Finnish Centre for Astronomy with ESO (FINCA), University of Turku, Vaisalantie 20, 21500, Piikkio, Finland3 Department of Physics, PO Box 64, 00014 University of Helsinki, Finland4 Observatory, 00014 University of Helsinki, Finland5 GRS mbH, 50667 Cologne, Germany

E-mail contact: hardee at rpi.edu

Chemical reactions in starless molecular clouds are heavily dependent on interactions between gas phase material andsolid phase dust and ices. We have observed the abundance and distribution of molecular gases in the cold, starlesscore DC 000.4-19.5 (SL42) in Corona Australis using data from the Swedish-ESO Submillimeter Telescope (SEST).We present column density maps determined from measurements of C18O (J = 2 − 1, 1 − 0) and N2H

+ (J = 1 − 0)emission features. Herschel data of the same region allow a direct comparison to the dust component of the cloud coreand provide evidence for gas phase depletion of CO at the highest extinctions. The dust color temperature in the corecalculated from Herschel maps ranges from roughly 10.7 to 14.0 K. This range agrees with the previous determinationsfrom Infrared Space Observatory (ISO) and Planck observations. The column density profile of the core can be fittedwith a Plummer-like density distribution approaching n(r) ∼ r−2 at large distances. The core structure deviatesclearly from a critical Bonnor-Ebert sphere. Instead, the core appears to be gravitationally bound and to lack thermaland turbulent support against the pressure of the surrounding low-density material: it may therefore be in the processof slow contraction. We test two chemical models and find that a steady-state depletion model (Keto and Caselli 2008,2010) agrees with the observed C18O column density profile and the observed N(C18O) vs. AV relationship.

Accepted by The Astrophysical Journal

Ammonia in the hot core W51-IRS2: 12 new maser lines and a maser component witha velocity drift

C. Henkel1,2, T. L. Wilson3, H. Asiri2, R. Mauersberger4

1 Max-Planck-Institut fur Radioastronomie, Auf dem Hugel 69, D-53121 Bonn, Germany2 Astronomy Department, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah, Saudi Arabia3 Naval Research Laboratory, Code 7210, Washington, DC 20375, USA4 Joint ALMA Observatory, Avda. Alonso de Cordova 3107, Vitacura, Santiago de Chile, Chile

E-mail contact: chenkel at mpifr-bonn.mpg.de

With the 100-m telescope at Effelsberg, 19 ammonia (NH3) maser lines have been detected toward the prominentmassive star forming region W51-IRS2. Twelve of these inversion lines, the (J,K) = (6,2), (5,3), (7,4), (8,5), (7,6),(8,6), (7,7), (9,7), (10,7), (9,9), (10,9), and (12,12) transitions, are classified as masers for the first time in outer space.The (7,7) line is the rst metastable (J = K) para-NH3 maser ever reported. All detected masers are related to highlyexcited inversion doublets. The (5,4) maser originates from an inversion doublet ∼340 K above the ground state,while the (12,12) transition, at ∼1450 K, is the most highly excited NH3 maser line so far known. Strong variabilityis seen not only in ortho- but also in para-NH3 transitions. Bright narrow emission features are observed, for the firsttime, in (mostly) ortho-ammonia transitions, at VLSR ∼ 45 km s−1, well separated from the quasi-thermal emissionnear 60 km s−1. These features were absent ∼25 years ago and show a velocity drift of about +0.2 km s−1 yr−1. Thecomponent is likely related to the SiO maser source in W51-IRS2 and a possible scenario explaining the velocity drift isoutlined. The 57 km s−1 component of the (9,6) maser line is found to be strongly linearly polarized. Maser emissionin the (J,K) to (J + 1,K) inversion doublets is strictly forbidden by selection rules for electric dipole transitions inthe ground vibrational state. However, such pairs (and even triplets with (J + 2,K)) are common toward W51-IRS2.Similarities in line widths and velocities indicate that such groups of maser lines arise from the same regions, whichcan be explained by pumping through vibrational excitation. The large number of NH3 maser lines in W51-IRS2 ismost likely related to the exceptionally high kinetic temperature and NH3 column density of this young massive starforming region.

Accepted for publication in Astronomy & Astrophysics

http://arxiv.org/pdf/1211.2484

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Protostellar Feedback and Final Mass of the Second-Generation Primordial Stars

Takashi Hosokawa1,2, Naoki Yoshida1,3, Kazuyuki Omukai4 and Harold W. Yorke2

1 Department of Physics, University of Tokyo, Japan2 Jet Propulsion Laboratory, California Institute of Technology, USA3 Kavli Institute for the Physics and Mathematics of the Universe, University of Tokyo, Japan4 Department of Physics, Kyoto University, Japan

E-mail contact: takashi.hosokawa at phys.s.u-tokyo.ac.jp

The first stars in the universe ionized the ambient primordial gas through various feedback processes. “Second-generation” primordial stars potentially form from this disturbed gas after its recombination. In this Letter, we studythe late formation stage of such second-generation stars, where a large amount of gas accretes onto the protostar andthe final stellar mass is determined when the accretion terminates. We directly compute the complex interplay betweenthe accretion flow and stellar ultraviolet (UV) radiation, performing radiation-hydrodynamic simulations coupled withstellar evolution calculations. Because of more efficient H2 and HD cooling in the pre-stellar stage, the accretion ratesonto the star are ten times lower than in the case of the formation of the first stars. The lower accretion rates andenvelope density result in the occurrence of an expanding bipolar HII region at a lower protostellar mass M∗ ≃ 10 M⊙,which blows out the circumstellar material, thereby quenching the mass supply from the envelope to the accretiondisk. At the same time the disk loses mass due to photoevaporation by the growing star. In our fiducial case thestellar UV feedback terminates mass accretion onto the star at M∗ ≃ 17 M⊙. Although the derived masses of thesecond-generation primordial stars are systematically lower than those of the first generation, the difference is withina factor of only a few. Our results suggest a new scenario, whereby the majority of the primordial stars are born asmassive stars with tens of solar masses, regardless of their generations.

Accepted by ApJ Letters (760:L37)

http://adsabs.harvard.edu/abs/2012ApJ...760L..37H

http://arxiv.org/pdf/1210.3035

CO bandhead emission of massive young stellar objects: determining disc properties

J. D. Ilee1, H. E. Wheelwright2, R. D. Oudmaijer1, W. J. de Wit3, L. T. Maud1, M. G. Hoare1, S. L.

Lumsden1, T. J. T. Moore4, J. S. Urquhart2 and J. C. Mottram5

1 School of Physics and Astronomy, EC Stoner Building, University of Leeds, Leeds, LS2 9JT, UK2 Max-Planck-Institut fur Radioastronomie, Auf dem Hugel 69, 53121, Bonn, Germany3 European Southern Observatory, Alonso de Cordova 3107, Vitacura, Santiago, Chile4 Astrophysics Research Institute, Liverpool JohnMoores University, Twelve Quays House, EgertonWharf, BirkenheadCH41 1LD5 Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, the Netherlands

E-mail contact: pyjdi at leeds.ac.uk

Massive stars play an important role in many areas of astrophysics, but numerous details regarding their formationremain unclear. In this paper we present and analyse high resolution (R ∼ 30,000) near-infrared 2.3 micron spectraof 20 massive young stellar objects from the RMS database, in the largest such study of CO first overtone bandheademission to date. We fit the emission under the assumption it originates from a circumstellar disc in Keplerian rotation.We explore three approaches to modelling the physical conditions within the disc - a disc heated mainly via irradiationfrom the central star, a disc heated mainly via viscosity, and a disc in which the temperature and density are describedanalytically. We find that the models described by heating mechanisms are inappropriate because they do not providegood fits to the CO emission spectra. We therefore restrict our analysis to the analytic model, and obtain good fits toall objects that possess sufficiently strong CO emission, suggesting circumstellar discs are the source of this emission.On average, the temperature and density structure of the discs correspond to geometrically thin discs, spread acrossa wide range of inclinations. Essentially all the discs are located within the dust sublimation radius, providing strongevidence that the CO emission originates close to the central protostar, on astronomical unit scales. In addition, weshow that the objects in our sample appear no different to the general population of MYSOs in the RMS database,based on their near- and mid-infrared colours. The combination of observations of a large sample of MYSOs with CObandhead emission and our detailed modelling provide compelling evidence of the presence of small scale gaseous discs

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around such objects, supporting the scenario in which massive stars form via disc accretion.

Accepted by MNRAS

http://arxiv.org/pdf/1212.0554

The standard model of low-mass star formation applied to massive stars:a multi-wavelength picture of AFGL 2591

K. G. Johnston1, D. S. Shepherd2, T. P. Robitaille1 and K. Wood3

1 Max Planck Institute for Astronomy, Konigstuhl 17, D-69117 Heidelberg, Germany2 National Radio Astronomy Observatory, 1003 Lopezville Rd, Socorro, New Mexico 87801, USA3 School of Physics & Astronomy, University of St Andrews, North Haugh, St Andrews, KY16 9SS, UK

E-mail contact: johnston at mpia.de

Context. While it is currently unclear from a theoretical standpoint which forces and processes dominate the formationof high-mass stars, and hence determine the mode in which they form, much of the recent observational evidencesuggests that massive stars are born in a similar manner to their low-mass counterparts.Aims. This paper aims to investigate the hypothesis that the embedded luminous star AFGL 2591-VLA 3 (2.3 x 105 L⊙

at 3.33 kpc) is forming according to a scaled-up version of a low-mass star formation scenario.Methods. We present multi-configuration Very Large Array 3.6 cm and 7 mm, as well as Combined Array for Researchin Millimeter Astronomy C18O and 3 mm continuum observations to investigate the morphology and kinematics ofthe ionized gas, dust, and molecular gas around AFGL 2591. We also compare our results to ancillary Gemini Northnear-IR images, and model the near-IR to sub-mm Spectral Energy distribution (SED) and Two Micron All SkySurvey (2MASS) image profiles of AFGL 2591 using a Monte-Carlo dust continuum radiative transfer code.Results. The observed 3.6 cm images uncover for the first time that the central powering source AFGL 2591-VLA 3has a compact core plus collimated jet morphology, extending 4000 AU eastward from the central source with anopening angle of < 10◦ at this radius. However, at 7 mm VLA 3 does not show a jet morphology, but instead compact(< 500 AU) emission, some of which (< 0.57 mJy of 2.9 mJy) is estimated to be from dust emission. The spectralindex of AFGL 2591-VLA 3 between 3.6 cm and 7 mm was found to be between 0.4 and 0.5, similar to that of anionized wind. If the 3.6 cm emission is modelled as an ionized jet, the jet has almost enough momentum to drive thelarger-scale flow. However, assuming a shock efficiency of 10%, the momentum rate of the jet is not sufficient to ionizeitself via only shocks, and thus a significant portion of the emission is instead likely created in a photoionized wind.The C18O emission uncovers dense entrained material in the outflow(s) from these young stars. The main features ofthe SED and 2MASS images of AFGL 2591-VLA 3 are also reproduced by our model dust geometry of a rotationallyflattened envelope with and without a disk.Conclusions. The above results are consistent with a picture of massive star formation similar to that seen for low-massprotostars. However, within its envelope, AFGL 2591-VLA 3 contains at least four other young stars, constituting asmall cluster. Therefore it appears that AFGL 2591-VLA 3 may be able to source its accreting material from a sharedgas reservoir while still exhibiting the phenomena expected during the formation of low-mass stars.

Accepted by A&A

http://www.mpia.de/homes/johnston/Johnston2012.pdf

High-dynamic-range extinction mapping of infrared dark clouds: Dependence of densityvariance with sonic Mach number in molecular clouds

Jouni Kainulainen1 and Jonathan C. Tan2,3

1 MPIA Heidelberg, Germany2 Dept. of Astronomy, University of Florida, Gainesville, USA3 Dept. of Physics, University of Florida, Gainesville, USA

E-mail contact: jtkainul at mpia.de

Measuring the mass distribution of infrared dark clouds (IRDCs) over the wide dynamic range of their column densitiesis a fundamental obstacle in determining the initial conditions of high-mass star formation and star cluster formation.We present a new technique to derive high-dynamic-range, arcsecond-scale resolution column density data for IRDCs

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and demonstrate the potential of such data in measuring the density variance - sonic Mach number relation in molecularclouds. We combine near-infrared data from the UKIDSS/Galactic Plane Survey with mid-infrared data from theSpitzer/GLIMPSE survey to derive dust extinction maps for a sample of ten IRDCs. We then examine the linewidthsof the IRDCs using 13CO line emission data from the FCRAO/Galactic Ring Survey and derive a column density -sonic Mach number relation for them. For comparison, we also examine the relation in a sample of nearby molecularclouds. The presented column density mapping technique provides a very capable, temperature independent toolfor mapping IRDCs over the column density range equivalent to AV ≃ 1 − 100 mag at a resolution of 2”. Usingthe data provided by the technique, we present the first direct measurement of the relationship between the columndensity dispersion, σN/〈N〉, and sonic Mach number, Ms, in molecular clouds. We detect correlation between thevariables with about 3-σ confidence. We derive the relation σN/〈N〉 ≈ (0.047± 0.016)Ms, which is suggestive of the

correlation coefficient between the volume density and sonic Mach number, σρ/〈ρ〉 ≈ (0.20+0.37−0.22)Ms, in which the

quoted uncertainties indicate the 3-σ range. When coupled with the results of recent numerical works, the existence ofthe correlation supports the picture of weak correlation between the magnetic field strength and density in molecularclouds (i.e., B ∝ ρ0.5). While our results remain suggestive because of the small number of clouds in our demonstrationsample, the analysis can be improved by extending the study to a larger number of clouds.

Accepted by Astronomy & Astrophysics

http://arxiv.org/pdf/1210.8130

Mean Motion Resonances in Exoplanet Systems: Investigation into Nodding Behavior

Jacob A. Ketchum1, Fred C. Adams1,2 and Anthony M. Bloch3

1 Physics Department, University of Michigan, Ann Arbor, MI 48109, USA2 Astronomy Department, University of Michigan, Ann Arbor, MI 48109, USA3 Department of Mathematics, University of Michigan, Ann Arbor, MI 48109, USA

E-mail contact: fca at umich.edu

Motivated by the large number of extrasolar planetary systems that are near mean motion resonances, this paperexplores a related type of dynamical behavior known as “nodding”. Here, the resonance angle of a planetary systemexecutes libration (oscillatory motion) for several cycles, circulates for one or more cycles, and then enters once againinto libration. This type of complicated dynamics can affect our interpretation of observed planetary systems thatare in or near mean motion resonance. This work shows that planetary systems in (near) mean motion resonance canexhibit nodding behavior, and outlines the portion of parameter space where it occurs. This problem is addressedusing both full numerical integrations of the planetary systems and via model equations obtained through expansionsof the disturbing function. In the latter approach, we identify the relevant terms that allow for nodding. The twoapproaches are in agreement, and show that nodding often occurs when a small body is in an external mean motionresonance with a larger planet. As a result, the nodding phenomenon can be important for interpreting observationsof transit timing variations, where the existence of smaller bodies is inferred through their effects on larger, observedtransiting planets. For example, in actively nodding planetary systems, both the amplitude and frequency of thetransit timing variations depend on the observational time window.

Accepted by The Astrophysical Journal

http://arxiv.org/pdf/1211.3078

On the effects of optically thick gas (disks) around massive stars

Rolf Kuiper1 and Harold W. Yorke1

1 Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA

E-mail contact: Rolf.Kuiper at jpl.nasa.gov

Numerical simulations have shown that the often cited radiation pressure barrier to accretion onto massive stars canbe circumvented, when the radiation field is highly anisotropic in the presence of a circumstellar accretion disk withhigh optical depth. Here, these studies of the so-called flashlight effect are expanded by including the opacity of theinnermost dust-free but potentially optically thick gas regions around forming massive stars. In addition to frequency-

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dependent opacities for the dust grains, we use temperature- and density-dependent Planck- and Rosseland meanopacities for the gas. The simulations show that the innermost dust-free parts of the accretion disks are opticallythick to the stellar radiation over a substantial fraction of the solid angle above and below the disk’s midplane. Thetemperature in the shielded disk region decreases faster with radius than in a comparison simulation with a lowerconstant gas opacity, and the dust sublimation front is shifted to smaller radii. The shielding by the dust-free gas inthe inner disk thus contributes to an enhanced flashlight effect, which ultimately results in a smaller opening angle ofthe radiation pressure driven outflow and in a much longer timescale of sustained feeding of the circumstellar disk bythe molecular cloud core. We conclude that it is necessary to properly account for the opacity of the inner dust-freedisk regions around forming massive stars in order to correctly assess the effectiveness of the flashlight effect, theopening angle of radiation pressure driven outflows, and the lifetime and morphological evolution of the accretion disk.

Accepted by ApJ

http://arxiv.org/pdf/1211.6432

Filamentary Star Formation: Observing the Evolution toward Flattened Envelopes

Katherine Lee1, Leslie Looney1, Doug Johnstone2,3, John Tobin4

1 Department of Astronomy, University of Illinois at Urbana-Champaign, 1002 W Green St, Urbana, IL 61801, USA2 Department of Physics and Astronomy, University of Victoria, P.O. Box 3055, STN CSC, Victoria, BC V8W 3P6,Canada3 NRC-Herzberg Institute of Astrophysics, 5071 West Saanich Road, Victoria, BC V9E 2E7, Canada4 Hubble Fellow, National Radio Astronomy Observatory, Charlottesville, VA 22903, USA

E-mail contact: ijlee9 at illinois.edu

Filamentary structures are ubiquitous from large-scale molecular clouds (few parsecs) to small-scale circumstellarenvelopes around Class 0 sources (∼1000 AU to ∼0.1 pc). In particular, recent observations with the Herschel SpaceObservatory emphasize the importance of large-scale filaments (few parsecs) and star formation. The small-scaleflattened envelopes around Class 0 sources are reminiscent of the large-scale filaments. We propose an observationallyderived scenario for filamentary star formation that describes the evolution of filaments as part of the process forformation of cores and circumstellar envelopes. If such a scenario is correct, small-scale filamentary structures (0.1 pcin length) with higher densities embedded in starless cores should exist, although to date almost all the interferometershave failed to observe such structures. We perform synthetic observations of filaments at the prestellar stage bymodeling the known Class 0 flattened envelope in L1157 using both the Combined Array for Research in Millimeter-wave Astronomy (CARMA) and the Atacama Large Millimeter/Submillimeter Array (ALMA). We show that withreasonable estimates for the column density through the flattened envelope, the CARMA D-array at 3mm wavelengthsis not able to detect such filamentary structure, so previous studies would not have detected them. However, thesubstructures may be detected with CARMA D+E array at 3 mm and CARMA E array at 1 mm as a result of moreappropriate resolution and sensitivity. ALMA is also capable of detecting the substructures and showing the structuresin detail compared to the CARMA results with its unprecedented sensitivity. Such detection will confirm the newproposed paradigm of non-spherical star formation.

Accepted by ApJ

http://arxiv.org/pdf/1211.0670

The Starburst Cluster Westerlund 1: The Initial Mass Function and Mass Segregation

Beomdu Lim1, Moo-Young Chun2, Hwankyung Sung1, Byeong-Gon Park2, Jae-Joon Lee2, Sangmo T.

Sohn3, Hyeonoh Hur1, and Michael S. Bessell4

1 Department of Astronomy and Space Science, Sejong University, 98 Gunja-dong, Gwangjin-gu, Seoul 143-747, Korea2 Korea Astronomy and Space Science Institute, 776 Daedeokdae-ro, Yusung-gu, Daejeon, Korea3 Space Telescope Science Institute, Baltimore, MD 21218, USA4 Research School of Astronomy and Astrophysics, Australian National University, MSO, Cotter Road, Weston, ACT2611, Australia

E-mail contact: bdlim1210 at sju.ac.kr

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Westerlund 1 is the most important starburst cluster in the Galaxy due to its massive star content. We have performedBVIc and JKs photometry to investigate the initial mass function (IMF). By comparing the observed color with thespectral type - intrinsic color relation, we obtain the mean interstellar reddening of <E(B-V)> = 4.19±0.23 and <E(J-Ks)> = 1.70± 0.21. Due to the heavy extinction toward the cluster, the zero-age main sequence fitting method basedon optical photometry proved to be inappropriate for the distance determination, while the near-infrared photometrygave a reliable distance to the cluster – 3.8 kpc from the empirical relation. Using the recent theoretical stellarevolution models with rotation, the age of the cluster is estimated to be 5.0±1.0 Myr. We derived the IMF in themassive part and obtained a fairly shallow slope of Γ = −0.8± 0.1. The integration of the IMF gave a total mass forthe cluster in excess of 5.0 × 104 solar mass. The IMF shows a clear radial variation indicating the presence of masssegregation. We also discuss the possible star formation history of Westerlund 1 from the presence of red supergiantsand relatively low-luminosity yellow hypergiants.

Accepted by the Astronomical Journal

http://arxiv.org/pdf/1211.5832

A Comparison of Approaches in Fitting Continuum SEDs

Yao Liu1, 2, 3, David Madlener3, Sebastian Wolf3, Hongchi Wang1

1 Purple Mountain Observatory, Chinese Academy of Sciences, 2 West Beijing Road, Nanjing 210008, China2 Graduate School of the Chinese Academy of Sciences, Beijing 100080, China3 Institut fur Theoretische Physik und Astrophysik, Universitat zu Kiel, Leibnizstr. 15, 24118 Kiel, Germany

E-mail contact: yliu at pmo.ac.cn

We present a detailed comparison of two approaches, the use of a pre-calculated database and simulated annealing (SA),for fitting the continuum spectral energy distribution (SED) of astrophysical objects whose appearance is dominatedby surrounding dust. While pre-calculated databases are commonly used to model SED data, only few studies todate employed SA due to its unclear accuracy and convergence time for this specific problem. From a methodologicalpoint of view, different approaches lead to different fitting quality, demand on computational resources and calculationtime. We compare the fitting quality and computational costs of these two approaches for the task of SED fitting toprovide a guide to the practitioner to find a compromise between desired accuracy and available resources. To reduceuncertainties inherent to real datasets, we introduce a reference model resembling a typical circumstellar system with10 free parameters. We derive the SED of the reference model with our code MC3D at 78 logarithmically distributedwavelengths in the range [0.3µm, 1.3mm] and use this setup to simulate SEDs for the database and SA. Our resultshows directly the applicability of SA in the field of SED modeling, since the algorithm regularly finds better solutionsto the optimization problem than a pre-calculated database. As both methods have advantages and shortcomings, ahybrid approach is preferable. While the database provides an approximate fit and overall probability distributionsfor all parameters deduced using Bayesian analysis, SA can be used to improve upon the results returned by the modelgrid.

Accepted by Research in Astronomy and Astrophysics

http://arxiv.org/pdf/1211.4309

ALMA and VLA observations of the outflows in IRAS 16293-2422

Laurent Loinard1,2, Luis A. Zapata1, Luis F. Rodriguez1, Gerardo Pech1, Claire J. Chandler3, Crystal

L. Brogan4, David J. Wilner5, Paul T. P. Ho5,6, Berengere Parise2, Lee W. Hartmann7, Zhaohuan Zhu8,

Satoko Takahashi6, and Alfonso Trejo6

1 Centro de Radiostronomıa y Astrofısica, Universidad Nacional Autonoma de Mexico, 58089 Morelia, Michoacan,Mexico2 Max-Planck-Institut fur Radioastronomie, Auf dem Hugel 69, 53121 Bonn, Germany3 National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801, USA4 National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903-2475, USA5 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA6 Academia Sinica Institute of Astronomy and Astrophysics, Taipei, Taiwan

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7 Department of Astronomy, University of Michigan, 500 Church St., Ann Arbor, MI 48109, USA8 Department of Astrophysical Sciences, 4 Ivy Lane, Peyton Hall, Princeton University, Princeton, NJ 08544, USA

We present ALMA and VLA observations of the molecular and ionized gas at 0.1′′–0.3′′ resolution in the Class0 protostellar system IRAS 16293-2422. These data clarify the origins of the protostellar outflows from the deeplyembedded sources in this complex region. Source A2 is confirmed to be at the origin of the well known large scale north-east–south-west flow. The most recent VLA observations reveal a new ejection from that protostar, demonstratingthat it drives an episodic jet. The central compact part of the other known large scale flow in the system, orientedroughly east-west, is well delineated by the CO (6-5) emission imaged with ALMA and is confirmed to be drivenfrom within component A. Finally, a one-sided blueshifted bubble-like outflow structure is detected here for the firsttime from source B to the north-west of the system. Its very short dynamical timescale (∼ 200 yr), low velocity, andmoderate collimation support the idea that source B is the youngest object in the system, and possibly one of theyoungest protostars known.

Accepted by MNRAS

http://arxiv.org/pdf/1211.4744

Herschel CHESS discovery of the fossil cloud that gave birth to the Trapezium andOrion KL

Ana Lopez-Sepulcre1, Mihkel Kama2, Cecilia Ceccarelli1, Carsten Dominik2,3, Emmanuel Caux4,5,

Asuncion Fuente6 and Tomas Alonso-Albi6

1 UJF-Grenoble 1 / CNRS-INSU, Institut de Planetologie et d’Astrophysique de Grenoble (IPAG) UMR 5274, Greno-ble, F-38041, France2 Astronomical Institute Anton Pannekoek, University of Amsterdam, Amsterdam, The Netherlands3 Department of Astrophysics/IMAPP, Radboud University Nijmegen, Nijmegen, The Netherlands4 Universite de Toulouse, UPS-OMP, IRAP, Toulouse, France5 CNRS, IRAP, 9 Av. colonel Roche, BP 44346, 31028 Toulouse Cedex 4, France6 Observatorio Astronomico Nacional, P.O. Box 112, 28803 Alcala de Henares, Madrid, Spain

E-mail contact: ana.sepulcre at obs.ujf-grenoble.fr

Context: The Orion A molecular complex is a nearby (420 pc), very well studied stellar nursery that is believed tocontain examples of triggered star formation.Aims : As part of the Herschel Guaranteed Time Key Programme CHESS, we present the discovery of a diffuse gascomponent in the foreground of the intermediate-mass protostar OMC-2 FIR 4, located in the Orion A region.Methods: Making use of the full HIFI spectrum of OMC-2 FIR 4 obtained in CHESS, we detected several ground-statelines from OH+, H2O

+, HF, and CH+, all of them seen in absorption against the dust continuum emission of theprotostar’s envelope. We derived column densities for each species, as well as an upper limit to the column density ofthe undetected H3O

+. In order to model and characterise the foreground cloud, we used the Meudon PDR code torun a homogeneous grid of models that spans a reasonable range of densities, visual extinctions, cosmic ray ionisationrates and far-ultraviolet (FUV) radiation fields, and studied the implications of adopting the Orion Nebula extinctionproperties instead of the standard interstellar medium ones.Results: The detected absorption lines peak at a velocity of 9 km s−1, which is blue-shifted by 2 km s−1 with respectto the systemic velocity of OMC-2 FIR 4 (VLSR = 11.4 km s−1). The results of our modelling indicate that theforeground cloud is composed of predominantly neutral diffuse gas (nH = 100 cm−3) and is heavily irradiated by anexternal source of FUV that most likely arises from the nearby Trapezium OB association. The cloud is 6 pc thickand bears many similarities with the so-called C+ interface between Orion-KL and the Trapezium cluster, 2 pc southof OMC-2 FIR 4.Conclusions: We conclude that the foreground cloud we detected is an extension of the C+ interface seen in thedirection of Orion KL, and interpret it to be the remains of the parental cloud of OMC-1, which extends from OMC-1up to OMC-2.

Accepted by Astronomy and Astrophysics

http://arxiv.org/pdf/1211.5772

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Millimeter Emission Structure in the first ALMA Image of the AU Mic Debris Disk

Meredith A. MacGregor1, David J. Wilner1, Katherine A. Rosenfeld1, Sean M. Andrews1, Brenda

Matthews2, A. Meredith Hughes3, Mark Booth2,4, Eugene Chiang3, James R. Graham3,5, Paul Kalas3,6,

Grant Kennedy7, and Bruce Sibthorpe8

1 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA2 Herzberg Institute of Astrophysics, 5072 West Saanich Road, Victoria, BC V9E 2E7, Canada3 Department of Astronomy, 601 Campbell Hall, University of California, Berkeley, CA 94720, USA4 Deptarment of Physics & Astronomy, University of Victoria, 3800 Finnerty Rd., Victoria, BC, V8P 5C2, Canada5 Dunlap Institute for Astronomy & Astrophysics, University of Toronto, Toronto, ON, Canada6 SETI Institute, 189 Bernardo Ave., Mountain View, CA 94043, USA7 Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK8 SRON Netherlands Institute for Space Research, NL-9747 AD Groningen, The Netherlands

We present 1.3 millimeter ALMA Cycle 0 observations of the edge-on debris disk around the nearby, ∼10 Myr-old,M-type star AU Mic. These observations obtain 0.6′′ (6 AU) resolution and reveal two distinct emission components:(1) the previously known dust belt that extends to a radius of 40 AU, and (2) a newly recognized central peak thatremains unresolved. The cold dust belt of mass about 1 lunar mass is resolved in the radial direction with a risingemission profile that peaks sharply at the location of the outer edge of the ”birth ring” of planetesimals hypothesizedto explain the midplane scattered light gradients. No significant asymmetries are discerned in the structure or positionof this dust belt. The central peak identified in the ALMA image is 6 times brighter than the stellar photosphere,which indicates an additional emission process in the inner regions of the system. Emission from a stellar corona oractivity may contribute, but the observations show no signs of temporal variations characteristic of radio-wave flares.We suggest that this central component may be dominated by dust emission from an inner planetesimal belt of massabout 0.01 lunar mass, consistent with a lack of emission shortward of 25 microns and a location <3 AU from thestar. Future millimeter observations can test this assertion, as an inner dust belt should be readily separated from thecentral star at higher angular resolution.

Accepted by ApJ Letters

http://arxiv.org/pdf/1211.5148

Subaru Imaging of Asymmetric Features in a Transitional Disk in Upper Scorpius

S. Mayama1,2, J. Hashimoto3, T. Muto4, T. Tsukagoshi5, N. Kusakabe3, M. Kuzuhara3,6, Y. Takahashi3,7,

T. Kudo8, R. Dong9, M. Fukagawa10, M. Takami11, M. Momose5, J. P. Wisniewski27, K. Follette15, L.

Abe12, E. Akiyama3, W. Brandner13, T. Brandt9, J. Carson14, S. Egner8, M. Feldt13, M. Goto29, C. A.

Grady16,17,18, O. Guyon8, Y. Hayano2,8, M. Hayashi2,3, S. Hayashi2,8, T. Henning13, K. W. Hodapp19, M.

Ishii8, M. Iye2,3, M. Janson9, R. Kandori3, J. Kwon2, G. R. Knapp9, T. Matsuo20, M. W. McElwain18,

S. Miyama21, J.-I. Morino3, A. Moro-Martin9,22, T. Nishimura8, T.-S. Pyo8, E. Serabyn23, H. Suto3, R.

Suzuki3, N. Takato2,8, H. Terada8, C. Thalmann24, D. Tomono8, E. L. Turner9,25, M. Watanabe26, T.

Yamada28, H. Takami2,8, T. Usuda2,8, M. Tamura2,3

1 The Center for the Promotion of Integrated Sciences, The Graduate University for Advanced Studies (SOKENDAI),Shonan International Village, Hayama-cho, Miura-gun, Kanagawa 240-0193, Japan2 Department of Astronomical Science, The Graduate University for Advanced Studies (SOKENDAI), 2-21-1 Osawa,Mitaka, Tokyo 181-8588, Japan3 National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan4 Division of Liberal Arts, Kogakuin University, 1-24-2, Nishi-Shinjuku, Shinjuku-ku, Tokyo, 163-8677, Japan5 College of Science, Ibaraki University, 2-1-1 Bunkyo, Mito, Ibaraki 310-8512, Japan6 Department of Earth and Planetary Science, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033,Japan7 Department of Astronomy, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan8 Subaru Telescope, 650 North A’ohoku Place, Hilo, HI 96720, USA9 Department of Astrophysical Sciences, Princeton University, NJ08544, USA10 Department of Earth and Space Science, Graduate School of Science, Osaka University, 1-1, Machikaneyama,Toyonaka, Osaka 560-0043, Japan

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11 Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 106, Taiwan12 Laboratoire Hippolyte Fizeau, UMR6525, Universite de Nice Sophia-Antipolis, 28, avenue Valrose, 06108 NiceCedex 02, France13 Max Planck Institute for Astronomy, Koenigstuhl 17, 69117 Heidelberg, Germany14 Department of Physics and Astronomy, College of Charleston, 58 Coming St., Charleston, SC 29424, USA.15 Department of Astronomy and Steward Observatory, The University of Arizona, 933 North Cherry Avenue, Rm.N204, Tucson, AZ 85721-0065, USA16 Goddard Center for Astrobiology, NASA’s Goddard Space Flight Center, Greenbelt, MD 20771, USA17 Eureka Scientific, 2452 Delmer, Suite 100, Oakland CA 96002, USA18 ExoPlanets and Stellar Astrophysics Laboratory, Code 667, Goddard Space Flight Center, Greenbelt, MD 20771USA19 Institute for Astronomy, University of Hawaii, 640 North A’ohoku Place, Hilo, HI 96720, USA20 Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto, 606-8502, Japan21 Office of the President, Hiroshima University, 1-3-2 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8511, JAPAN22 Departamento de Astrofisica, CAB (INTA-CSIC), Instituto Nacional de Tecnica Aeroespacial, Torrejon de Ardoz,28850, Madrid, Spain23 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA24 Astronomical Institute ”Anton Pannekoek”, University of Amsterdam, Science Park 904, 1098 XH Amsterdam,The Netherlands25 Institute for the Physics and Mathematics of the Universe, The University of Tokyo, Kashiwa 227-8568, Japan26 Department of Cosmosciences, Hokkaido University, Sapporo 060-0810, Japan27 H L Dodge Department of Physics & Astronomy, University of Oklahoma, 440 W Brooks St. Norman, OK 73019,USA28 Astronomical Institute, Tohoku University, Aoba, Sendai 980-8578, Japan29 Universitats-Sternwarte Munchen Scheinerstr. 1, D-81679 Munich, Germany

E-mail contact: mayama satoshi at soken.ac.jp

We report high-resolution (0.07 arcsec) near-infrared polarized intensity images of the circumstellar disk around thestar 2MASS J16042165-2130284 obtained with HiCIAO mounted on the Subaru 8.2 m telescope. We present ourH-band data, which clearly exhibits a resolved, face-on disk with a large inner hole for the first time at infraredwavelengths. We detect the centrosymmetric polarization pattern in the circumstellar material as has been observedin other disks. Elliptical fitting gives the semimajor axis, semiminor axis, and position angle of the disk as 63 AU,62 AU, and -14 ◦, respectively. angle of -14 ◦. The disk is asymmetric, with one dip located at position angles of∼85◦. Our observed disk size agrees well with a previous study of dust and CO emission at submm wavelength withSMA. Hence, the near-infrared light is interpreted as scattered light reflected from the inner edge of the disk. Ourobservations also detect an elongated arc (50 AU) extending over the disk inner hole. It emanates at the inner edgeof the western side of the disk, extending inward first, then curving to the northeast. We discuss the possibility thatthe inner hole, the dip, and the arc that we have observed may be related to the existence of unseen bodies within thedisk.

Accepted by ApJL (760:L26)

http://iopscience.iop.org/2041-8205/760/2/L26/

http://arxiv.org/pdf/1211.3284

A Double-Jet System in the G31.41+0.31 Hot Molecular Core

Luca Moscadelli1, Jing Li Jing2, Riccardo Cesaroni1, Alberto Sanna3, Ye Xu2 and Qizhou Zhang4

1 INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy2 Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008, China3 Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, 53121 Bonn, Germany4 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA

E-mail contact: mosca at arcetri.astro.it

Many aspects of massive star (>∼10 M⊙) formation are still unclear. In particular, the outflow properties at closedistance (100–1000 AU) from a “Massive Young Stellar Object” (MYSO) are not yet well established. This work

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presents a detailed study of the gas kinematics towards the “Hot Molecular Core” (HMC) G31.41+0.31. To study theHMC 3-D kinematics at milli-arcsecond angular resolution, we have performed multi-epoch VLBI observations of theH2O 22 GHz and CH3OH 6.7 GHz masers, and single-epoch VLBI of the OH 1.6 GHz masers. Water masers present asymmetric spatial distribution with respect to the HMC center, where two nearby (0.2′′ apart), compact, VLA sources(labeled “A” and “B”) are previously detected. The spatial distribution of a first group of water masers, named “J1”,is well fit with an elliptical profile, and the maser proper motions mainly diverge from the ellipse center, with averagespeed of 36 km s−1. These findings strongly suggest that the “J1” water maser group traces the heads of a young(dynamical time of 1.3 103 yr), powerful (momentum rate of ≃ 0.2 M⊙ yr−1 km s−1), collimated (semi-opening angle≃ 10◦) jet emerging from a MYSO located close (within ≈0.15′′) to the VLA source “B”. Most of the water featuresnot belonging to “J1” present an elongated (≈2′′ in size), NE–SW oriented (PA≈70◦), S-shape distribution, which wedenote with the label “J2”. The elongated distribution of the “J2” group and the direction of motion, approximatelyparallel to the direction of elongation, of most “J2” water masers suggests the presence of another collimated outflow,emitted from a MYSO placed near the VLA source “A”. The proper motions of the CH3OH 6.7 GHz masers, mostlydiverging from the HMC center, also witness the expansion of the HMC gas driven by the “J1” and “J2” jets. Theorientation (PA≈70◦) of the “J2” jet agrees well with that (PA = 68◦) of the well-defined VLSR gradient across theHMC revealed by previous interferometric, thermal line observations. Furthermore, the “J2” jet is powerful enoughto sustain the large momentum rate, 0.3 M⊙ yr−1 km s−1, estimated from the interferometric, molecular line datain the assumption that the VLSR gradient represents a collimated outflow. These two facts lead us to favour theinterpretation of the VLSR gradient across the G31.41+0.31 HMC in terms of a compact and collimated outflow.

Accepted by Astronomy & Astrophysics

http://arxiv.org/pdf/1211.2667

Dynamics of Core Accretion

Andrew F. Nelson1 and Maximilian Ruffert2

1 XCP-2 MS T087, Los Alamos National Laboratory, Los Alamos NM, 87545, USA2 School of Mathematics and Maxwell Institute, University of Edinburgh, Edinburgh Scotland EH9 3JZ

E-mail contact: andy.nelson at lanl.gov

We perform 3-dimensional hydrodynamic simulations of gas flowing around a planetary core of mass Mpl=10M⊕

embedded in a near Keplerian background flow, using a modified shearing box approximation. We assume an ideal gasbehavior following an equation of state with a fixed ratio of the specific heats, γ = 1.42, consistent with the conditionsof a moderate temperature background disk with solar composition. No radiative heating or cooling is included in themodels. We employ a nested grid hydrodynamic code implementing the ‘Piecewise Parabolic Method’ with as manyas six fixed nested grids, providing spatial resolution on the finest grid comparable to the present day diameters ofNeptune and Uranus.We find that a strongly dynamically active flow develops such that no static envelope can form. The activity is notsensitive to plausible variations in the rotation curve of the underlying disk. It is sensitive to the thermodynamictreatment of the gas, as modeled by prescribed equations of state (either ‘locally isothermal’ or ‘locally isentropic’)and the temperature of the background disk material. The activity is also sensitive to the shape and depth of thecore’s gravitational potential, through its mass and gravitational softening coefficient. Each of these factors influencethe magnitude and character of hydrodynamic feedback of the small scale flow on the background, and we concludethat accurate modeling of such feedback is critical to a complete understanding of the core accretion process.The varying flow pattern gives rise to large, irregular eruptions of matter from the region around the core which returnmatter to the background flow: mass in the envelope at one time may not be found in the envelope at any later time.No net mass accretion into the envelope is observed over the course of the simulation and none is expected, due toour neglect of cooling. Except in cases of very rapid cooling however, as defined by locally isothermal or isentropictreatments, any cooling that does affect the envelope material will have limited consequences for the dynamics, sincethe flow quickly carries cooled material out of the core’s environment entirely. The angular momentum of materialin the envelope, relative to the core, varies both in magnitude and in sign on time scales of days to months nearthe core and on time scales a few years at distances comparable to the Hill radius. The dynamical activity contrastswith the largely static behavior typically assumed within the framework of the core accretion model for Jovian planetformation.

34

We show that material entering the dynamically active environment may suffer intense heating and cooling events thedurations of which are as short as a few hours to a few days. Shorter durations are not observable in our work due tothe limits of our resolution. Peak temperatures in these events range from T ∼ 1000 K to as high as T ∼ 3− 4000 K,with densities ρ ∼ 10−9 − 10−8 g/cm3. These time scales, densities and temperatures span a range consistent withthose required for chondrule formation in the nebular shock model. We therefore propose that dynamical activity inthe Jovian planet formation environment could be responsible for the production of chondrules and other annealedsilicates in the solar nebula.

Accepted by MNRAS

http://arxiv.org/pdf/1211.5423

Ortho–H2 and the age of prestellar cores

Laurent Pagani1, Pierre Lesaffre2, Mohammad Jorfi3, Pascal Honvault4,5, Tomas Gonzalez-Lezana6 and

Alexandre Faust7

1 LERMA, UMR8112 du CNRS, Observatoire de Paris, 61, Av. de l’Observatoire, 75014 Paris, France2 LERMA, UMR8112 du CNRS, Ecole Normale Superieure, 24 rue Lhomond, 75231 Paris Cedex 05, France3 Institut de Chimie des Milieux et des Materiaux de Poitiers, UMR CNRS 6503, Universite de Poitiers, 86022 PoitiersCedex, France4 Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 du CNRS, Universite de Bourgogne, 21078 DijonCedex, France5 UFR Sciences et Techniques, Universite de Franche-Comte, 25030 Besancon cedex, France6 Instituto de Fısica Fundamental, CSIC, Serrano 123, 28006 Madrid, Spain7 Institut de Planetologie et d’Astrophysique de Grenoble, UMR 5274 du CNRS, Universite Joseph Fourier, B.P. 53,38041 Grenoble Cedex 09, France

E-mail contact: laurent.pagani at obspm.fr

Prestellar cores form from the contraction of cold gas and dust material in dark clouds before they collapse to formprotostars. Several concurrent theories exist to describe this contraction which are currently difficult to discriminate.One major difference is the time scale involved to form the prestellar cores: some theories advocate nearly free-fallspeed via e.g. rapid turbulence decay while others can accommodate much longer periods to let the gas accumulatevia e.g. ambipolar diffusion. To discriminate between these theories, measuring the age of prestellar cores couldgreatly help. However, no reliable clock currently exists. We present a simple chemical clock based on the regulationof the deuteration by the abundance of ortho–H2 that slowly decays away from the ortho–para statistical ratio of 3down to or less than 0.001. We use a chemical network fully coupled to a hydrodynamical model which follows thecontraction of a cloud, starting from uniform density, and reaches a density profile typical of a prestellar core. Wecompute the N2D

+/N2H+ ratio along the density profile. The disappearance of ortho–H2 is tied to the duration of

the contraction and the N2D+/N2H

+ ratio increases in the wake of the ortho–H2 abundance decrease. By adjustingthe time of contraction, we obtain different deuteration profiles that we can compare to the observations. Our modelcan test fast contractions (from 104 to 106 cm−3 in ∼0.5 My) and slow contraction (from 104 to 106 cm−3 in ∼5My). We have tested the sensitivity of the models to various initial conditions. The slow contraction deuterationprofile is approximately insensitive to these variations while the fast contraction deuteration profile shows significantvariations. We found that in all cases, the deuteration profile remains clearly distinguishable whether it comes fromthe fast collapse or the slow collapse. We also study the para–D2H

+/ortho–H2D+ ratio and find that its variation

is not monotonic and therefore not discriminant between models. Applying this model to L183 (= L134N), we findthat the N2D

+/N2H+ ratio would be larger than unity for evolutionary timescales of a few megayears independently

of other parameters such as, e.g., cosmic ray ionization rate or grain size (within reasonable ranges). A good fit to theobservations is obtained for fast contraction only (≤ 0.7 My from the beginning of the contraction and ≤ 4 My fromthe birth of the molecular cloud based on the necessity to keep a high ortho–H2 abundance when the contraction starts– ortho–H2/para–H2 ≥ 0.2 – to match the observations). This chemical clock therefore rules out slow contraction inL183 and steady state chemical models, as steady state is clearly not reached here. This clock should be applied toother cores to help discriminate between slow and fast contraction theories over a large sample of cases.

Accepted by A&A

For preprints, please, contact 1st author

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Early stages of cluster formation: fragmentation of massive dense cores down to 1000AU

Aina Palau1, Asuncion Fuente2, Josep M. Girart1, Robert Estalella3, Paul T. P. Ho4,5, Alvaro Sanchez-

Monge6, Francesco Fontani6, Gemma Busquet7, Benoıt Commercon8, Patrick Hennebelle8, Jeremie

Boissier9,10, Qizhou Zhang4, Riccardo Cesaroni6, Luis A. Zapata11

1 Institut de Ciencies de l’Espai, Campus UAB Facultat de Ciencies, Torre C5 parell 2, 08193 Bellaterra, Catalunya,Spain2 Observatorio Astronomico Nacional, P.O. Box 112, 28803 Alcala de Henares, Madrid, Spain3 Departament d’Astronomia i Meteorologia (IEEC-UB), Institut de Ciencies del Cosmos, Universitat de Barcelona,Mart Franques, 1, 08028 Barcelona, Spain4 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA5 Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 106, Taiwan6 Osservatorio Astrofisico di Arcetri, INAF, Lago E. Fermi 5, 50125, Firenze, Italy7 INAF-Istituto di Astrofisica e Planetologia Spaziali, Areadi Recerca di Tor Vergata, Via Fosso Cavaliere 100, 00133,Roma, Italy8 Laboratoire de Radioastronomie, UMR CNRS 8112, Ecole Normale Superieure et Observatoire de Paris, 24 rueLhomond, 75231 Paris Cedex 05, France9 Istituto di Radioastronomia, INAF, Via Gobetti 101, Bologna, Italy10 ESO, Karl Schwarzschild St. 2, 85748 Garching Muenchen, Germany11 Centro de Radioastronomıa y Astrofsica, Universidad Nacional Autonoma de Mxico, P.O. Box 3-72, 58090, Morelia,Michoacan, Mexico

E-mail contact: palau at ieec.uab.es

In order to study the fragmentation of massive dense cores, which constitute the cluster cradles, we observed withthe PdBI in the most extended configuration the continuum at 1.3 mm and the CO(2-1) emission of four massivecores. We detect dust condensations down to ∼0.3 M⊙ and separate millimeter sources down to 0.4′′ or ∼1000 AU,comparable to the sensitivities and separations reached in optical/infrared studies of clusters. The CO(2-1) highangular resolution images reveal high-velocity knots usually aligned with previously known outflow directions. This,in combination with additional cores from the literature observed at similar mass sensitivity and spatial resolution,allowed us to build a sample of 18 protoclusters with luminosities spanning 3 orders of magnitude. Among the 18regions, ∼30% show no signs of fragmentation, while 50% split up into ∼4 millimeter sources. We compiled a list ofproperties for the 18 massive dense cores, such as bolometric luminosity, total mass, and mean density, and foundno correlation of any of these parameters with the fragmentation level. In order to investigate the combined effectsof magnetic field, radiative feedback and turbulence in the fragmentation process, we compared our observations toradiation magneto-hydrodynamic simulations, and found that the low-fragmented regions are well reproduced in themagnetized core case, while the highly-fragmented regions are consistent with cores where turbulence dominates overthe magnetic field. Overall, our study suggests that the fragmentation in massive dense cores could be determined bythe initial magnetic field/turbulence balance in each particular core.

Accepted by ApJ

http://arxiv.org/pdf/1211.2666

Herschel view of the Taurus B211/3 filament and striations: Evidence of filamentarygrowth?

P. Palmeirim1, Ph. Andre1, J. Kirk2, D. Ward-Thompson3, D. Arzoumanian1, V. Konyves1,4, P.

Didelon1, N. Schneider1,5, M. Benedettini6, S. Bontemps5, J. Di Francesco7,8, D. Elia6, M. Griffin2, M.

Hennemann1, T. Hill1, P. G. Martin9, A. Men’shchikov1, S. Molinari6, F. Motte1, Q. Nguyen Luong9,

D. Nutter2, N. Peretto1, S. Pezzuto6, A. Roy9, K. L. J. Rygl6, L. Spinoglio6 and G. L. White10,11

1 Laboratoire AIM, CEA/DSM–CNRS–Universite Paris Diderot, IRFU/Service d’Astrophysique, C.E.A. Saclay, Ormedes Merisiers, 91191 Gif-sur-Yvette, France2 School of Physics & Astronomy, Cardiff University, Cardiff, UK3 Jeremiah Horrocks Institute, University of Central Lancashire, PR1 2HE, UK4 Institut d’Astrophysique Spatiale, UMR 8617, CNRS/Universite Paris-Sud 11, 91405 Orsay, France

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5 Universite de Bordeaux, Laboratoire d’Astrophysique de Bordeaux, CNRS/INSU, UMR 5804, BP 89, 33271 FloiracCedex, France6 INAF - IAPS, via Fosso del Cavaliere 100, I-00133 Roma, Italy7 National Research Council of Canada, Herzberg Institute of Astrophysics, 5071 West Saanich Road, Victoria BC,V9E 2E7, Canada8 Department of Physics and Astronomy, University of Victoria, PO Box 355, STN CSC, Victoria BC, V8W 3P6,Canada9 Canadian Institute for Theoretical Astrophysics, University of Toronto, 60 St. George Street, Toronto, ON, M5S3H8, Canada10 Space Science and Technology Department, STFC Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire,OX11 0QX, UK11 Department of Physics and Astronomy, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK

E-mail contact: pedro.palmeirim at cea.fr

We present first results from the Herschel Gould Belt survey for the B211/L1495 region in the Taurus molecularcloud. Thanks to their high sensitivity and dynamic range, the Herschel images reveal the structure of the dense,star-forming filament B211 with unprecedented detail, along with the presence of striations perpendicular to thefilament and generally oriented along the magnetic field direction as traced by optical polarization vectors. Based onthe column density and dust temperature maps derived from the Herschel data, we find that the radial density profileof the B211 filament approaches power-law behavior, ρ ∝ r−2.0±0.4, at large radii and that the temperature profileexhibits a marked drop at small radii. The observed density and temperature profiles of the B211 filament are in goodagreement with a theoretical model of a cylindrical filament undergoing gravitational contraction with a polytropicequation of state: P ∝ ργ and T ∝ ργ−1, with γ=0.97±0.01<1 (i.e., not strictly isothermal). The morphology ofthe column density map, where some of the perpendicular striations are apparently connected to the B211 filament,further suggests that the material may be accreting along the striations onto the main filament. The typical velocitiesexpected for the infalling material in this picture are ∼ 0.5–1 km/s, which are consistent with the existing kinematicalconstraints from previous CO observations.

Accepted by Astronomy and Astrophysics

http://arxiv.org/pdf/1211.6360

Local-Density Driven Clustered Star Formation

Genevieve Parmentier1 and Susanne Pfalzner2

1 Zentrum fur Astronomie, Heidelberg Universitat, Germany2 Max-Planck Institut fur Radioastronomie, Bonn, Germany

E-mail contact: gparm at ari.uni-heidelberg.de

A positive power-law trend between the local surface densities of molecular gas, Σgas, and young stellar objects, Σ⋆,in molecular clouds of the Solar Neighbourhood has recently been identified by Gutermuth et al. How it relates to theproperties of embedded clusters, in particular to the recently established radius-density relation, has so far not beeninvestigated. In this paper, we model the development of the stellar component of molecular clumps as a functionof time and initial local volume density so as to provide a coherent framework able to explain both the molecular-cloud and embedded-cluster relations quoted above. To do so, we associate the observed volume density gradient ofmolecular clumps to a density-dependent free-fall time. The molecular clump star formation history is obtained byapplying a constant SFE per free-fall time, ǫff .For volume density profiles typical of observed molecular clumps (i.e. power-law slope ≃ −1.7), our model gives astar-gas surface-density relation Σ⋆ ∝ Σ2

gas, in very good agreement with the Gutermuth et al relation. Taking thecase of a molecular clump of mass M0 ≃ 104Msun and radius R ≃ 6pc experiencing star formation during 2 Myr, wederive what SFE per free-fall time matches best the normalizations of the observed and predicted (Σ⋆, Σgas) relations.We find ǫff ≃ 0.1. We show that the observed growth of embedded clusters, embodied by their radius-density relation,corresponds to a surface density threshold being applied to developing star-forming regions. The consequences of ourmodel in terms of cluster survivability after residual star-forming gas expulsion are that due to the locally high SFEin the inner part of star-forming regions, global SFE as low as 10% can lead to the formation of bound gas-free starclusters.

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Accepted by Astronomy & Astrophysics

http://arxiv.org/pdf/1211.1383

Warm water deuterium fractionation in IRAS 16293-2422 – The high-resolution ALMAand SMA view

Magnus V. Persson1,2, Jes K. Jørgensen2,1 and Ewine F. van Dishoeck3,4

1 Centre for Star and Planet Formation, Natural History Museum of Denmark, University of Copenhagen, ØsterVoldgade 5-7, DK-1350, Copenhagen K, Denmark2 Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen Ø, Denmark3 Leiden Observatory, Leiden University, P.O. Box 9513, NL-2300 RA Leiden, The Netherlands4 Max-Planck Institute fur extraterrestrische Physik (MPE), Giessenbachstrasse, 85748 Garching, Germany

E-mail contact: magnusp at nbi.dk

Measuring the water deuterium fractionation in the inner warm regions of low-mass protostars has so far been ham-pered by poor angular resolution obtainable with single-dish ground- and space-based telescopes. Observations ofwater isotopologues using (sub)millimeter wavelength interferometers have the potential to shed light on this matter.Observations toward IRAS 16293-2422 of the 53,2 − 44,1 transition of H18

2 O at 692.07914 GHz from Atacama LargeMillimeter/submillimeter Array (ALMA) as well as the 31,3 − 22,0 of H18

2 O at 203.40752 GHz and the 31,2 − 22,1transition of HDO at 225.89672 GHz from the Submillimeter Array (SMA) are presented. The 692 GHz H18

2 O line isseen toward both components of the binary protostar. Toward one of the components, “source B”, the line is seen inabsorption toward the continuum, slightly red-shifted from the systemic velocity, whereas emission is seen off-sourceat the systemic velocity. Toward the other component, “source A”, the two HDO and H18

2 O lines are detected aswell with the SMA. From the H18

2 O transitions the excitation temperature is estimated at 124± 12 K. The calculatedHDO/H2O ratio is (9.2± 2.6)× 10−4 – significantly lower than previous estimates in the warm gas close to the source.It is also lower by a factor of ∼5 than the ratio deduced in the outer envelope. Our observations reveal the physicaland chemical structure of water vapor close to the protostars on solar-system scales. The red-shifted absorption de-tected toward source B is indicative of infall. The excitation temperature is consistent with the picture of water iceevaporation close to the protostar. The low HDO/H2O ratio deduced here suggests that the differences between theinner regions of the protostars and the Earth’s oceans and comets are smaller than previously thought.

Accepted by Astronomy & Astrophysics Letters

http://arxiv.org/pdf/1211.6605

Constraining mass ratio and extinction in the FU Orionis binary system with infraredintegral field spectroscopy

Laurent Pueyo1, Lynne Hillenbrand2, Gautam Vasisht3, Ben R. Oppenheimer4, John D. Monnier5,

Sasha Hinkley2, Justin Crepp7, Lewis C. Roberts Jr3, Douglas Brenner4, Neil Zimmerman4, Ian Parry8,

Charles Beichman6, Richard Dekany2, Mike Shao3, Rick Burruss3, Eric Cady3, Jenny Roberts2, and

Remi Soummer1

1 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA2 Department of Astronomy, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125, USA3 Jet propulsion Laboratory, California Institute of technology, 4800 Oak Grove Drive, Pasadena, CA 91109 , USA4 American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024, USA5 Department of Astronomy, University of Michigan, 941 Dennison Building, 500 Church Street, Ann Arbor, MI48109-1090, USA6 NASA Exoplanet Science Institute, 770 S. Wilson Avenue, Pasadena, CA 91225, USA7 Department of Physics, 225 Nieuwland Science Hall, University of Notre Dame, Notre Dame, IN 46556, USA8 University of Cambridge, Institute of Astronomy, Madingley Rd, Cambridge, CB3 0HA, UK

We report low resolution near infrared spectroscopic observations of the eruptive star FU Orionis using the IntegralField Spectrograph Project 1640 installed at the Palomar Hale telescope. This work focuses on elucidating the natureof the faint source, located 0.5′′ south of FU Ori, and identified in 2003 as FU Ori S. We first use our observations

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in conjunction with published data to demonstrate that the two stars are indeed physically associated and form atrue binary pair. We then proceed to extract J and H band spectro-photometry using the damped LOCI algorithm,a reduction method tailored for high contrast science with IFS. This is the first communication reporting the highaccuracy of this technique, pioneered by the Project 1640 team, on a faint astronomical source. We use our lowresolution near infrared spectrum in conjunction with 10.2 micron interferometric data to constrain the infrared excessof FU Ori S. We then focus on estimating the bulk physical properties of FU Ori S. Our models lead to estimates ofan object heavily reddened, AV = 8-12, with an effective temperature of ∼ 4000–6500 K . Finally we put these resultsin the context of the FU Ori N-S system and argue that our analysis provides evidence that FU Ori S might be themore massive component of this binary system.

Accepted by ApJ (757:A57)

http://arxiv.org/pdf/1211.6741

The Co-ordinated Radio and Infrared Survey for High-Mass Star Formation - II. SourceCatalogue

C. R. Purcell1,2,3, M. G. Hoare1, W. D. Cotton4, S. L. Lumsden1, J. S. Urquhart1,5,6, C. Chandler7,

E. B. Churchwell8, P. Diamond2, 5, S. M. Dougherty9, R. P. Fender10, G. Fuller2, S. T. Garrington2,

T. M. Gledhill11, P. F. Goldsmith12, L. Hindson5,11, J. M. Jackson13, S. E. Kurtz14, J. Martı15,

T. J. T. Moore16, L. G. Mundy17, T. W. B. Muxlow2, R. D. Oudmaijer1, J. D. Pandian18, J. M. Paredes19,

D. S. Shepherd7,20, S. Smethurst2, R. E. Spencer2, M. A. Thompson11, G. Umana21 and A. A. Zijlstra2

1 School of Physics & Astronomy, E.C. Stoner Building, University of Leeds, Leeds LS2 9JT, UK2 Jodrell Bank Centre for Astrophysics, The Alan Turing Building, School of Physics and Astronomy, The Universityof Manchester, Oxford Rd, Manchester, M13 9PL, UK3 Sydney Institute for Astronomy (SiFA), School of Physics, The University of Sydney, NSW 2006, Australia4 National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903-2475, USA5 CSIRO Astronomy and Space Science, PO BOX 76, Epping, NSW 1710, Australia6 Max-Planck-Institut fur Radioastronomie, Auf dem Hugel 69, D-53121 Bonn, Germany7 National Radio Astronomy Observatory, Array Operations Center, P.O. Box O, 1003 Lopezville Road, Socorro, NM87801-0387, USA8 The University of Wisconsin, Department of Astronomy, 475 North Charter Street Madison, WI 53706, USA9 National Research Council of Canada, Herzberg Institute for Astrophysics, Dominion Radio Astrophysical Observa-tory, PO Box 248, Penticton, British Columbia V2A 6J9, Canada10 School of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ, UK11 Science and Technology Research Institute, University of Hertfordshire, College Lane, Hatfield AL10 9AB, UK12 Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, California 91109, USA13 Astronomy Department, Boston University, 725 Commonwealth Avenue, Boston, MA 02215, USA14 Centro de Radioastronomıa y Astrofısica, Universidad Nacional Autonoma de Mexico - Morelia, Apartado Postal3-72, C.P. 58090 Morelia, Michoacan, Mexico15 Departamento de Fısica, EPSJ, Universidad de Jaen, Campus Las Lagunillas s/n, Edif. A3, 23071 Jaen, Spain16 Astrophysics Research Institute, Liverpool John Moores University, Twelve Quays House, Egerton Wharf, Birken-head CH41 1LD, UK17 Department of Astronomy, University of Maryland College Park, MD 20742-2421, USA18 Institute for Astronomy, 2680 Woodlawn Drive, Honolulu, Hawaii 96822-1839, USA19 Departament d’Astronomia i Meteorologia and Institut de Ciencies del Cosmos (ICC), Universitat de Barcelona(UB/IEEC), Martı Franqus 1, 08028 Barcelona, Spain20 Square Kilometer Array - South Africa, 3rd floor, The Park, Park Rd, Pinelands, Cape Town, 7405 Western Cape,South Africa21 INAF Osservatorio Astrofisico di Catania, via S. Sofia 78, 95123 Catania, Italy

E-mail contact: C.R.Purcell at leeds.ac.uk

The CORNISH project is the highest resolution radio continuum survey of the Galactic plane to date. It is the5GHz radio continuum part of a series of multi-wavelength surveys that focus on the northern GLIMPSE region(10◦ < l < 65◦), observed by the Spitzer satellite in the mid-infrared. Observations with the Very Large Array in B

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and BnA configurations have yielded a 1.5′′ resolution Stokes I map with a root-mean-squared noise level better than0.4mJybeam−1. Here we describe the data-processing methods and data characteristics, and present a new, uniformcatalogue of compact radio-emission. This includes an implementation of automatic deconvolution that provides muchmore reliable imaging than standard CLEANing. A rigorous investigation of the noise characteristics and reliabilityof source detection has been carried out. We show that the survey is optimised to detect emission on size scales upto 14′′ and for unresolved sources the catalogue is more than 90 percent complete at a flux density of 3.9mJy. Wehave detected 3,062 sources above a 7σ detection limit and present their ensemble properties. The catalogue is highlyreliable away from regions containing poorly-sampled extended emission, which comprise less than two percent of thesurvey area. Imaging problems have been mitigated by down-weighting the shortest spacings and potential artefactsflagged via a rigorous manual inspection with reference to the Spitzer infrared data. We present images of the mostcommon source types found: H II regions, planetary nebulae and radio-galaxies. The CORNISH data and catalogueare available online at http://cornish.leeds.ac.uk.

Accepted by ApJ. Sup.

http://arxiv.org/pdf/1211.7116

13CO Cores in the Taurus Molecular Cloud

Lei Qian1, Di Li1,2,3 and Paul Goldsmith4

1 National Astronomical Observatories, CAS, Beijing, 100012, China2 Space Science Institute, Boulder, CO, USA3 Department of Astronomy, California Institute of Technology, CA, USA4 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA

E-mail contact: lqian at nao.cas.cn

Young stars form in molecular cores, which are dense condensations within molecular clouds. We have searched formolecular cores traced by 13CO J = 1 → 0 emission in the Taurus molecular cloud and studied their properties. Ourdata set has a spatial dynamic range (the ratio of linear map size to the pixel size) of about 1000 and spectrallyresolved velocity information, which together allow a systematic examination of the distribution and dynamic stateof 13CO cores in a large contiguous region. We use empirical fit to the CO and CO2 ice to correct for depletion ofgas-phase CO. The 13CO core mass function (13CO CMF) can be fitted better with a log-normal function than witha power-law function. We also extract cores and calculate the 13CO CMF based on the integrated intensity of 13COand the CMF from Two Micron All Sky Survey. We demonstrate that core blending exists, i.e., combined structuresthat are incoherent in velocity but continuous in column density. The core velocity dispersion (CVD), which is thevariance of the core velocity difference δv, exhibits a power-law behavior as a function of the apparent separation L:CVD (km s−1) v ∝ L(pc)0.7. This is similar to Larson’s law for the velocity dispersion of the gas. The peak velocitiesof 13CO cores do not deviate from the centroid velocities of the ambient 12CO gas by more than half of the line width.The low velocity dispersion among cores, the close similarity between CVD and Larson’s law, and the small separationbetween core centroid velocities and the ambient gas all suggest that molecular cores condense out of the diffuse gaswithout additional energy from star formation or significant impact from converging flows.

Accepted by Astrophysical Journal

http://arxiv.org/pdf/1206.2115v3

Proper Motions of Young Stellar Outflows in the Mid-Infrared with Spitzer (IRAC). I.The NGC 1333 region

A. C. Raga1, A. Noriega-Crespo2, S. J. Carey3, H. G. Arce4

1 Instituto de Ciencias Nucleares, UNAM, Ap. 70-543, 04510 D.F., Mexico2 Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125, USA3 Spitzer Science Center, California Institute of Technology, Pasadena, CA 91125, USA4 Department of Astronomy, Yale University, New Haven, CT 06520, USA Draft version November 5, 2012

E-mail contact: raga at nucleares.unam.mx

We use two 4.5 micron Spitzer (IRAC) maps of the NGC 1333 region taken over a ∼ 7 yr interval to determine

40

proper motions of its associated outflows. This is a first, successful attempt at obtaining proper motions of stellaroutflow from Spitzer observations. For the outflow formed by the Herbig-Haro objects HH7, 8 and 10, we find propermotions of ∼ 9–13 km s−1, which are consistent with previously determined optical proper motions of these objects.We determine proper motions for a total of 8 outflows, ranging from ∼ 10 to 100 km s−1. The derived proper motionsshow that out of these 8 outflows, 3 have tangential velocities ≤ to 20 km s−1. This result shows that a large fractionof the observed outflows have low intrinsic velocities, and that the low proper motions are not merely a projectioneffect.

Accepted by the Astronomical Journal

http://arxiv.org/pdf/1211.0273

Mini-Oort clouds: Compact isotropic planetesimal clouds from planet-planet scattering

Sean N. Raymond1,2 and Philip J. Armitage3,4

1 CNRS, UMR 5804, Laboratoire d’Astrophysique de Bordeaux, 2 rue de l’Observatoire, BP 89, F-33271 FloiracCedex, France2 Universite de Bordeaux, Observatoire Aquitain des Sciences de l’Univers, 2 rue de l’Observatoire, BP 89, F-33271Floirac Cedex, France3 JILA, University of Colorado & NIST, 440 UCB, Boulder CO 80309-0440, USA4 Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, USA

E-mail contact: rayray.sean at gmail.com

Starting from planetary systems with three giant planets and an outer disk of planetesimals, we use dynamicalsimulations to show how dynamical instabilities can transform planetesimal disks into 100-1000 AU-scale isotropicclouds. The instabilities involve a phase of planet-planet scattering that concludes with the ejection of one or moreplanets and the inward-scattering of the surviving gas giant(s) to remove them from direct dynamical contact with theplanetesimals. ”Mini-Oort clouds” are thus formed from scattered planetesimals whose orbits are frozen by the abruptdisappearance of the perturbing giant planet. Although the planetesimal orbits are virtually isotropic, the survivinggiant planets tend to have modest inclinations (typically ∼10 degrees) with respect to the initial orbital plane. Thecollisional lifetimes of mini-Oort clouds are long (10 Myr to >10 Gyr) and there is a window of ∼100 Myr or longerduring which they produce spherical clouds of potentially observable dust at 70 microns. If the formation channel forhot Jupiters commonly involves planetary close encounters, we predict a correlation between this subset of extrasolarplanetary systems and mini-Oort clouds.

Accepted to MNRAS Letters

http://arxiv.org/pdf/1211.2809

New Young Star Candidates in BRC 27 and BRC 34

L. M. Rebull1, C. H. Johnson2, J. C. Gibbs3, M. Linahan4, D. Sartore5, R. Laher1, M. Legassie1,6, J. D.

Armstrong7, L. E. Allen8, P. McGehee9 D. L. Padgett10 S. Aryal3, K. S. Badura5, T. S. Canakapalli3,

S. Carlson2, M. Clark2, N. Ezyk4, J. Fagan4, N. Killingstad2, S. Koop2, T. McCanna2, M. M. Nishida3,

T. R. Nuthmann3, A. O’Bryan2, A. Pullinger4, A. Rameswaram4, T. Ravelomanantsoa2, H. Sprow4,

C. M. Tilley5

1 Spitzer Science Center/Caltech, M/S 220-6, 1200 E. California Blvd., Pasadena, CA 91125, USA2 Breck School, 123 Ottawa Ave. N., Golden Valley, MN 55422 USA3 Glencoe High School, 2700 NW Glencoe Rd., Hillsboro, OR 97124 USA4 Carmel Catholic High School, One Carmel Parkway, Mundelein, IL 60060, USA5 Pine Ridge High School, 926 Howland Blvd., Deltona, FL 32738 USA6 Raytheon Mission Operations and Services, 299 N. Euclid Ave, Pasadena, CA, 91101 USA7 Las Cumbres Observatory Global Telescope (LCOGT) & University of Hawaii, HI, USA8 NOAO, Tucson, AZ, USA9 IPAC, M/S 220-6, 1200 E. California Blvd., Pasadena, CA 91125, USA10 NASA’s Goddard Space Flight Center, 8800 Greenbelt Rd., Greenbelt, MD, 20771, USA

E-mail contact: rebull@ipac.caltech.edu

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We used archival Spitzer Space Telescope mid-infrared data to search for young stellar objects (YSOs) in the immediatevicinity of two bright-rimmed clouds, BRC 27 (part of CMa R1) and BRC 34 (part of the IC 1396 complex). Theseregions both appear to be actively forming young stars, perhaps triggered by the proximate OB stars. In BRC 27,we find clear infrared excesses around 22 of the 26 YSOs or YSO candidates identified in the literature, and identify16 new YSO candidates that appear to have IR excesses. In BRC 34, the one literature-identified YSO has an IRexcess, and we suggest 13 new YSO candidates in this region, including a new Class I object. Considering the entireensemble, both BRCs are likely of comparable ages, within the uncertainties of small number statistics and withoutspectroscopy to confirm or refute the YSO candidates. Similarly, no clear conclusions can yet be drawn about anypossible age gradients that may be present across the BRCs.

Accepted by Astron. J.

http://web.ipac.caltech.edu/~rebull/papers/brc1.pdf

A Search for Herbig-Haro Objects in NGC 7023 and Barnard 175

Travis Rector1 and Heidi Schwieker2

1 University of Alaska Anchorage, Dept. of Physics and Astronomy, Anchorage, AK 99508 USA2 National Optical Astronomy Observatory, Tucson, AZ 85719, USA

E-mail contact: rector at uaa.alaska.edu

Wide-field optical imaging was obtained of the cluster and reflection nebula NGC 7023 and the Bok globule B175.We report the discovery of four new Herbig-Haro (HH) objects in NGC 7023, the first HH objects to be found in thisregion. They were first detected by their Hα and [S II] emission but are also visible at 3.6 and 4.5 µm in archivalSpitzer observations of this field. These HH objects are part of at least two distinct outflows. Both outflows are alignedwith embedded “Class I” YSOs in a tight group on the western edge of the nebula. One of the outflows may have aprojected distance of 0.75pc, which is a notable length for an embedded source.No new HH objects were discovered in B175. However, we reclassify the knot HH450X, in B175, as a backgroundgalaxy. The discovery that HH 450X is not a shock front weakens the argument that HH 450 and SNR G110.3+11.3are co-located and interacting.

Accepted by AJ

http://arxiv.org/pdf/1211.7190

Formation of the Widest Binaries from Dynamical Unfolding of Triple Systems

Bo Reipurth1 and Seppo Mikkola2

1 Institute for Astronomy, Univ. of Hawaii at Manoa, 640 N. Aohoku Place, HI 96720, USA2 Tuorla Observatory, University of Turku, Vaisalantie 20, Piikkio, Finland

E-mail contact: reipurth at ifa.hawaii.edu

The formation of very wide binaries, such as the α Cen system with Proxima (also known as α Centauri C) separatedfrom α Centauri (which itself is a close binary A/B) by 15000 AU, challenges current theories of star formation,because their separation can exceed the typical size of a collapsing cloud core. Various hypotheses have been proposedto overcome this problem, including the suggestion that ultra-wide binaries result from the dissolution of a star cluster– when a cluster star gravitationally captures another, distant, cluster star. Recent observations have shown that verywide binaries are frequently members of triple systems and that close binaries often have a distant third companion.Here we report Nbody simulations of the dynamical evolution of newborn triple systems still embedded in their nascentcloud cores that match observations of very wide systems. We find that although the triple systems are born verycompact – and therefore initially are more protected against disruption by passing stars – they can develop extremehierarchical architectures on timescales of millions of years as one component is dynamically scattered into a verydistant orbit. The energy of ejection comes from shrinking the orbits of the other two stars, often making them lookfrom a distance like a single star. Such loosely bound triple systems will therefore appear to be very wide binaries.

Accepted by Nature (Dec 13, 2012 issue)

http://arxiv.org/pdf/1212.1246

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ALMA observations of rho-Oph 102: grain growth and molecular gas in the disk arounda young Brown Dwarf

L. Ricci, L. Testi, A. Natta, A. Scholz, and I. de Gregorio-Monsalvo

1 Department of Astronomy, California Institute of Technology, MC 249-17, Pasadena, CA 91125, USA2 European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching, Germany3 INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125 Firenze, Italy4 School of Cosmic Physics, Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2, Ireland5 Joint ALMA Observatory (JAO)/ESO, Alonso de Cordova 3107. Vitacura 763 0335. Santiago de Chile

E-mail contact: lricci at astro.caltech.edu

We present ALMA continuum and spectral line observations of the young Brown Dwarf rho-Oph 102 at about 0.89mm and 3.2 mm. We detect dust emission from the disk at these wavelengths and derive an upper limit on the radiusof the dusty disk of ∼ 40 AU. The derived variation of the dust opacity with frequency in the mm provides evidencefor the presence of mm-sized grains in the disk outer regions. This result demonstrates that mm-grains are found evenin the low density environments of Brown Dwarf disks and challenges our current understanding of dust evolution indisks. The CO map at 345 GHz clearly reveals molecular gas emission at the location of the Brown Dwarf, indicatinga gas-rich disk as typically found for disks surrounding young pre-Main Sequence stars. We derive a disk mass of ∼0.3–1% of the mass of the central Brown Dwarf, similar to the typical values found for disks around more massiveyoung stars.

Accepted by ApJ Letters

http://arxiv.org/pdf/1211.6743

Circum-planetary discs as bottlenecks for gas accretion onto giant planets

Guillaume Rivier1,2, Aurelien Crida1, Alessandro Morbidelli1, Yann Brouet1,3

1 Laboratoire Lagrange, UMR7293, Universite de Nice Sophia-antipolis/CNRS/Observatoire de la Cote d’Azur, B.P.4229, 06304 Nice Cedex 4, France2 Formation Supaero, Institut Superieur de l’Aeronautique et de l’Espace, 10 av. Edouard Belin, B.P. 94235, 31400Toulouse Cedex 4, France3 Laboratoire LERMA/Observatoire de Paris, 61 avenue de l’Observatoire, 75014, Paris, France

With hundreds of exoplanets detected, it is necessary to revisit giant planets accretion models to explain their massdistribution. In particular, formation of sub-jovian planets remains unclear, given the short timescale for the runawayaccretion of massive atmospheres. However, gas needs to pass through a circum-planetary disc. If the latter has a lowviscosity (as expected if planets form in ”dead zones”), it might act as a bottleneck for gas accretion. We investigatewhat the minimum accretion rate is for a planet under the limit assumption that the circum-planetary disc is totallyinviscid, and the transport of angular momentum occurs solely because of the gravitational perturbations from thestar. To estimate the accretion rate, we present a steady-state model of an inviscid circum-planetary disc, with verticalgas inflow and external torque from the star. Hydrodynamical simulations of a circum-planetary disc were conductedin 2D, in a planetocentric frame, with the star as an external perturber in order to measure the torque exerted bythe star on the disc. The disc shows a two-armed spiral wave caused by stellar tides, propagating all the way in fromthe outer edge of the disc towards the planet. The stellar torque is small and corresponds to a doubling time for aJupiter mass planet of the order of 5 Myrs. Given the limit assumptions, this is clearly a lower bound of the realaccretion rate. This result shows that gas accretion onto a giant planet can be regulated by circum-planetary discs.This suggests that the diversity of masses of extra-solar planets may be the result of different viscosities in these discs.

Accepted by Astronomy and Astrophysics

http://arxiv.org/pdf/1211.1820

Tracing large-scale structures in circumstellar disks with ALMA

Jan Philipp Ruge1, Sebastian Wolf1, Ana L. Uribe2,3 and Hubert H. Klahr2

1 Universitat zu Kiel, Institut fur Theoretische und Astrophysik, Leibnitzstr. 15, 24098 Kiel, Germany2 Max-Planck-Institut fur Astronomie, Konigstuhl 17, 69117 Heidelberg, Germany

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3 University of Chicago, The Department of Astronomy and Astrophysics, 5640 S. Ellis Ave, Chicago, IL 60637, USA

E-mail contact: ruge at astrophysik.uni-kiel.de

Context. Planets are supposed to form in circumstellar disks. The additional gravitational potential of a planetperturbs the disk and leads to characteristic structures, i.e. spiral waves and gaps, in the disk’s density profile.Aims. We perform a large-scale parameter study of the observability of these planet-induced structures in circumstellardisks in the (sub)mm wavelength range for the Atacama Large (Sub)Millimeter Array (ALMA).Methods. On the basis of hydrodynamical and magneto-hydrodynamical simulations of star-disk-planet models, wecalculated the disk temperature structure and (sub)mm images of these systems. These were used to derive simulatedALMA images. Because appropriate objects are frequent in the Taurus-Auriga region, we focused on a distance of140 pc and a declination of ≈ 20◦. The explored range of star-disk-planet configurations consists of six hydrodynamicalsimulations (including magnetic fields and different planet masses), nine disk sizes with outer radii ranging from 9AUto 225AU, 15 total disk masses in the range between 2.67 · 10−7M⊙ and 4.10 · 10−2M⊙, six different central stars,and two different grain size distributions, resulting in 10 000 disk models.Results. On almost all scales and in particular down to a scale of a few AU, ALMA is able to trace disk structuresinduced by planet-disk interaction or by the influence of magnetic fields on the wavelength range between 0.4 and2.0mm. In most cases, the optimum angular resolution is limited by the sensitivity of ALMA. However, withinthe range of typical masses of protoplanetary disks (0.1M⊙ − −0.001M⊙) the disk mass has a minor impact on the

observability. It is possible to resolve disks down to 2.67 ·10−6M⊙ and trace gaps induced by a planet withMp

M⋆

= 0.001

in disks with 2.67 · 10−4M⊙ with a signal-to-noise ratio greater than three. The central star has a major impact onthe observability of gaps, as well as on the considered maximum grainsize of the dust in the disk. In general, it ismore likely to trace planet-induced gaps in our magnetohydrodynamical disk models, because gaps are wider in thepresence of magnetic fields. We also find that zonal flows resulting from magneto-rotational instability (MRI) creategap-like structures in the disk’s re-emission radiation, which are observable with ALMA.Conclusions. Through the unprecedented resolution and sensitivity of ALMA in the (sub)mm wavelength range, theexpected detailed observations of planet-disk interaction and global disk structures will deepen our understanding ofthe planet formation and disk evolution process.

Accepted by A&A

Initial phases of massive star formation in high infrared extinction clouds. II. Infall andonset of star formation

K. L. J. Rygl1,2, F. Wyrowski2, F. Schuller3,2, K. M. Menten2

1 Istituto di Astrofisica e Planetologia Spaziali, Via del Fosso del Cavaliere 100, 00133 Roma, Italy2 Max-Planck-Institut fur Radioastronomie, Auf dem Hugel 69, 53121 Bonn, Germany3 European Southern Observatory, Alonso de Cordova 3107, Casilla 19001, Santiago 19, Chile

E-mail contact: kazi.rygl at inaf.it

The onset of massive star formation is not well understood because of observational and theoretical difficulties. To findthe dense and cold clumps where massive star formation can take place, we compiled a sample of high infrared extinctionclouds. We observed the clumps in these high extinction clouds in the 1.2mm continuum emission and ammonia withthe goals of deriving the masses, densities, temperatures, and kinematic distances. We try to understand the star-formation stages of the high extinction clumps by studying their infall and outflow properties, the presence of a youngstellar object (YSO), and the level of the CO depletion. Are the physical parameters, density, mass, temperature,and column density correlated with the star-forming properties? Does the cloud morphology, quantified throughthe column density contrast between the clump and the clouds, have an impact on the evolution of star formationoccurring inside it? Star-formation properties, such as infall, outflow, CO depletion, and the presence of YSOs, werederived from a molecular line survey performed with the IRAM 30m and the APEX 12m telescopes. We find thatthe HCO+(1–0) transition is the most sensitive for detecting infalling motions. SiO, an outflow tracer, was mostlydetected toward sources with infall, indicating that infall is accompanied by collimated outflows. We calculated infallvelocities from the line profiles and found them to be of the order of 0.3–7km s−1. The presence of YSOs within aclump depends mostly on the clump column density; no indication of YSOs were found below 4 × 1022 cm−2. Starformation is on the verge of beginning in clouds that have a low column density contrast; the infall is not yet present inthe majority of the clumps. The first signs of ongoing star formation are broadly observed in clouds where the column

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density contrast between the clump and the cloud is higher than two; most clumps show infall and outflow. Finally,we find the most evolved clumps in clouds that have a column density contrast higher than three; in many clumps,the infall has already halted, and toward most clumps we found indications of YSOs. Hence, the cloud morphology,based on the column density contrast between the cloud and the clumps, seems to have a direct connection with theevolutionary stage of the objects forming inside.

Accepted by Astronomy and Astrophysics

http://arxiv.org/pdf/1210.2063

Recent star formation in the Lupus clouds as seen by Herschel

K. L. J. Rygl1, M. Benedettini1, E. Schisano1, D. Elia1, S. Molinari1, S. Pezzuto1, Ph. Andre2, J. P.

Bernard3, G. J. White4,5, D. Polychroni6,1, S. Bontemps7,2, N. L. J. Cox8, J. Di Francesco9,10, A.

Facchini1, C. Fallscheer9,10, A. M. di Giorgio1, M. Hennemann2, T. Hill2, V. Konyves2, V. Minier2, F.

Motte2, Q. Nguyen-Luong11, N. Peretto2, M. Pestalozzi1, S. Sadavoy9,10, N. Schneider7,2, L. Spinoglio1,

L. Testi12,13, D. Ward-Thompson14

1 Istituto di Astrofisica e Planetologia Spaziali, via del Fosso del Cavaliere 100, 00133 Roma, Italy2 Laboratoire AIM Paris-Saclay, CEA/IRFU CNRS/INSU Universite Paris Diderot, 91191 Gif-sur-Yvette, France3 CESR, Observatoire Midi-Pyrnes (CNRS-UPS), Universite de Toulouse, BP 44346, 31028 Toulouse, France4 Rutherford Appleton LIbrary, Chilton, Didcot, OX11 0NL, UK5 Department of Physics and Astronomy, Open University, Milton Keynes, UK6 University of Athens, Department of Astrophysics, Astronomy and Mechanics, Faculty of Physics, Panepistimiopolis,15784 Zografos, Athens, Greece7 CNRS/INSU, Laboratoire d’Astrophysique de Bordeaux UMR 5904, BP 89, 33271 Floirac, France8 Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium9 Department of Physics and Astronomy, University of Victoria, PO Box 355, STN CSC, Victoria BC Canada, V8W3P610 National Research Council Canada, Herzberg Institute of Astrophysics, 5071 West Saanich Road, Victoria BCCanada, V9E 2E711 Canadian Institute for Theoretical Astrophysics (CITA), University of Toronto, 60 St. George Street, Toronto ONCanada, M5S 3H812 European Southern Observatory, Karl-Schwarzschild-Strasse 2, 87548 Garching bei Munchen, Germany13 INAF-Osservatorio Astrofisico di Arcetri, Large E. Fermi 5, 50125 Firenze, Italy14 Jeremiah Horrocks Institute, University of Central Lancashire, PR1 2HE, UK

E-mail contact: kazi.rygl at inaf.it

We present a study of the star formation histories of the Lupus I, III, and IV clouds using the Herschel 70–500µmmaps obtained by the Herschel Gould Belt Survey Key Project. By combining the new Herschel data with the existingSpitzer catalog we obtained an unprecedented census of prestellar sources and young stellar objects in the Lupus clouds,which allowed us to study the overall star formation rate (SFR) and efficiency (SFE). The high SFE of Lupus III, itsdecreasing SFR, and its large number of pre-main sequence stars with respect to proto- and prestellar sources, suggestthat Lupus III is the most evolved cloud, and after having experienced a major star formation event in the past, isnow approaching the end of its current star-forming cycle. Lupus I is currently undergoing a large star formationevent, apparent by the increasing SFR, the large number of prestellar objects with respect to more evolved objects,and the high percentage of material at high extinction (e.g., above AV ≈ 8mag). Also Lupus IV has an increasingSFR; however, the relative number of prestellar sources is much lower, suggesting that its star formation has not yetreached its peak.

Accepted by Astronomy and Astrophysics Letters

http://arxiv.org/pdf/1211.5232

The Initial Mass Function and the Surface Density Profile of NGC 6231

Hwankyung Sung1, Hugues Sana2, and M. S. Bessell3

1 Department of Astronomy and Space Science, Sejong University, 98, Kunja-dong, Kwangjin-gu, Seoul 143-747, Korea2 Astronomical Institute ’Anton Pannekeok’, Amsterdam University, Science Park 904, 1098 XH, Amsterdam, The

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Netherlands3 Research School of Astronomy and Astrophysics, Australian National University, MSO, Cotter Road, Weston, ACT2611, Australia

E-mail contact: sungh at sejong.ac.kr

We have performed new wide-field photometry of the young open cluster NGC 6231 to study the shape of the initialmass function (IMF) and mass segregation. We also investigated the reddening law toward NGC 6231 from optical tomid-infrared color excess ratios, and found that the total-to-selective extinction ratio is RV = 3.2, which is very closeto the normal value. But many early-type stars in the cluster center show large color excess ratios. We derived thesurface density profiles of four member groups, and found that they reach the surface density of field stars at about 10′,regardless of stellar mass. The IMF of NGC 6231 is derived for the mass range 0.8 – 45 M⊙. The slope of the IMF ofNGC 6231 (Γ = −1.1± 0.1) is slightly shallower than the canonical value, but the difference is marginal. In addition,the mass function varies systematically, and is a strong function of radius - it is very shallow at the center, and verysteep at the outer ring suggesting the cluster is mass segregated. We confirm the mass segregation for the massivestars (m >∼ 8 M⊙) by a minimum spanning tree analysis. Using a Monte Carlo method, we estimate the total massof NGC 6231 to be about 2.6(±0.6)× 103M⊙. We constrain the age of NGC 6231 by comparison with evolutionaryisochrones. The age of the low-mass stars ranges from 1 to 7 Myr with a slight peak at 3 Myr. However the age of thehigh mass stars depends on the adopted models and is 3.5 ± 0.5 Myr from the non- or moderately-rotating models ofBrott et al. as well as the non-rotating models of Ekstrom et al. But the age is 4.0 – 7.0 Myr if the rotating models ofEkstrom et al. are adopted. This latter age is in excellent agreement with the time scale of ejection of the high massrunaway star HD 153919 from NGC 6231, albeit the younger age cannot be entirely excluded.

Accepted by the Astronomical Journal

http://arxiv.org/pdf/1211.4278

Hierarchical Fragmentation of the Orion Molecular Filaments

Satoko Takahashi1, Paul T. P. Ho1,2, Paula S. Teixeira3,4, Luis A. Zapata5 and Yu-Nung Su1

1 Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-131, Taipei, Taiwan2 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street Cambridge, MA 02138, USA3 Universitaet Wien, Institut fuer Astrophysik, Tuerkenschanzstrasse 17, 1180, Wien, Austria4 Laboratorio Associado Instituto D. Luiz-SIM, Universidade de Lisboa, Campo Grande, 1749-016, Lisbon, Portugal5 Centro de Radioastronomıa y Astrofısica, Universidad Nacional Autonoma de Mexico, Morelia, Michoacan 58090,Mexico

E-mail contact: satoko t at asiaa.sinica.edu.tw

We present a high angular resolution map of 850 µm continuum emission of the Orion Molecular Cloud-3 (OMC3) obtained with the Submillimeter Array (SMA); the map is a mosaic of 85 pointings covering an approximatearea of 6′.5×2′.0 (0.88×0.27 pc). We detect 12 spatially resolved continuum sources, each with an H2 mass between0.3–5.7 M⊙ and a projected source size between 1400–8200 AU. All the detected sources are on the filamentary mainridge (nH2

≥106 cm−3), and analysis based on the Jeans theorem suggests that they are most likely gravitationallyunstable. Comparison of multi-wavelength data sets indicates that of the continuum sources, 6/12 (50 %) are associatedwith molecular outflows, 8/12 (67 %) are associated with infrared sources, and 3/12 (25 %) are associated with ionizedjets. The evolutionary status of these sources ranges from prestellar cores to protostar phase, confirming that OMC-3is an active region with ongoing embedded star-formation. We detect quasi-periodical separations between the OMC-3 sources of ≈17′′/0.035 pc. This spatial distribution is part of a large hierarchical structure, that also includesfragmentation scales of GMC (≈35 pc), large-scale clumps (≈1.3 pc), and small-scale clumps (≈0.3 pc), suggestingthat hierarchical fragmentation operates within the Orion A molecular cloud. The fragmentation spacings are roughlyconsistent with the thermal fragmentation length in large-scale clumps, while for small-scale cores it is smaller thanthe local fragmentation length. These smaller spacings observed with the SMA can be explained by either a helicalmagnetic field, cloud rotation, or/and global filament collapse. Finally, possible evidence for sequential fragmentationis suggested in the northern part of the OMC-3 filament.

Accepted by Astrophysical Journal

http://arxiv.org/pdf/1211.6842

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A 0.2 solar mass protostar with a Keplerian disk in the very young L1527 IRS system

John J. Tobin1, Lee Hartmann2, Hsin-Fang Chiang3,4, David J. Wilner5, Leslie W. Looney3, Laurent

Loinard6,7, Nuria Calvet2 and Paola D’Alessio6

1 Hubble Fellow, National Radio Astronomy Observatory, Charlottesville, VA2 University of Michigan3 University of Illinois4 Institute for Astronomy, University of Hawaii at Manoa5 Harvard-Smithsonian Center for Astrophysics6 Centro de Radioastronomia y Astrofisica, UNAM7 Max-Planck-Institut fur Radioastronomie

E-mail contact: jtobin at nrao.edu

In their earliest stages, protostars accrete mass from their surrounding envelopes through circumstellar disks. Untilnow, the smallest observed protostar/envelope mass ratio was ∼2.1. The protostar L1527 IRS is thought to be in theearliest stages of star formation. Its envelope contains ∼1 solar mass of material within a ∼0.05 pc radius, and earlierobservations suggested the presence of an edge-on disk. Here we report observations of dust continuum emission and13CO (J = 2 → 1) line emission from the disk around L1527, from which we determine a protostellar mass of M∗

= 0.19 ± 0.04 solar masses and a protostar/envelope mass ratio of ∼0.2. We conclude that most of the luminosityis generated through the accretion process, with an accretion rate of ∼6.6× 10−7 solar masses yr−1. If it has beenaccreting at that rate through much of its life, its age is ∼300,000 yr, though theory suggests larger accretion ratesearlier, so it may be younger. The presence of a rotationally–supported disk is confirmed and significantly more massmay be added to its planet-forming region as well as the protostar itself.

Accepted by Nature (Dec 5, 2012 issue)

http://www.cv.nrao.edu/~jtobin/L1527-nature.pdf

Tearing the Veil: interaction of the Orion Nebula with its neutral environment

Paul P. van der Werf1,2, W. M. Goss3, C. R. O’Dell4

1 Leiden Observatory, Leiden University, P.O. Box 9513, NL 2300 RA Leiden, The Netherlands2 SUPA, Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ,United Kingdom3 National Radio Astronomy Observatory, P.O. Box 0, Socorro, NM 87801, USA4 Department of Physics and Astronomy, Vanderbilt University, Box 1807-B, Nashville, TN 37235, USA

E-mail contact: pvdwerf at strw.leidenuniv.nl

We present HI 21cm observations of the Orion Nebula, obtained with the Karl G. Jansky Very Large Array, at anangular resolution of 7.2′′×5.7′′ and a velocity resolution of 0.77 km s−1. Our data reveal HI absorption towards theradio continuum of the HII region, and HI emission arising from the Orion Bar photon-dominated region (PDR) andfrom the Orion-KL outflow. In the Orion Bar PDR, the HI signal peaks in the same layer as the H2 near-infraredvibrational line emission, in agreement with models of the photodissociation of H2. The gas temperature in this regionis approximately 540 K, and the HI abundance in the interclump gas in the PDR is 5–10% of the available hydrogennuclei. Most of the gas in this region therefore remains molecular. Mechanical feedback on the Veil manifests itselfthrough the interaction of ionized flow systems in the Orion Nebula, in particular the Herbig-Haro object HH202, withthe Veil. These interactions give rise to prominent blueward velocity shifts of the gas in the Veil. The unambiguousevidence for interaction of this flow system with the Veil shows that the distance between the Veil and the Trapeziumstars needs to be revised downwards to about 0.4 pc. The depth of the ionized cavity is about 0.7 pc, which is muchsmaller than the depth and the lateral extent of the Veil. Our results reaffirm the blister model for the M42 HII region,while also revealing its relation to the neutral environment on a larger scale.

Accepted for publication in the Astrophysical Journal

http://arxiv.org/pdf/1211.0470

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Distance and Kinematics of the TW Hydrae Association from Parallaxes

Alycia J. Weinberger1, Guillem Anglada-Escude2, Alan P. Boss3

1 Department of Terrestrial Magnetism, Carnegie Institution of Washington 5241 Broad Branch Road NW, Washing-ton, DC 20015, USA2 Universitat Gottingen, Institut fur Astrophysik Friedrich-Hund-Platz 1, 37077 Gottingen, Germany3 Department of Terrestrial Magnetism, Carnegie Institution of Washington 5241 Broad Branch Road NW, Washing-ton, DC 20015, USA

E-mail contact: weinberger at dtm.ciw.edu

From common proper motion and signatures of youth, researchers have identified about 30 members of a putative TWHydrae Association. Only four of these had parallactic distances from Hipparcos. We have measured parallaxes andproper motions for 14 primary members. We combine these with literature values of radial velocities to show that theGalactic space motions of the stars, with the exception of TWA 9 and 22, are parallel and do not indicate convergenceat a common formation point sometime in the last few million years. The space motions of TWA 9 and 22 do notagree with the others and indicate that they are not TWA members. The median parallax is 18 mas or 56 pc. Wefurther analyze the stars’ absolute magnitudes on pre-main sequence evolutionary tracks and find a range of ages witha median of 10.1 Myr and no correlation between age and Galactic location. The TWA stars may have formed froman extended and filamentary molecular cloud but are not necessarily precisely coeval.

Accepted by ApJ

http://arxiv.org/pdf/1211.2233

Massive Star Formation, Outflows, and Anomalous H2 Emission in Mol 121 (IRAS20188+3928)

Grace Wolf-Chase1,2, Kim Arvidsson1, Michael Smutko3 and Reid Sherman2

1 Astronomy Department, Adler Planetarium, 1300 S. Lake Shore Dr., Chicago, IL 60605, USA2 Department of Astronomy & Astrophysics, University of Chicago, 5640 S. Ellis Ave., Chicago, IL 60637, USA3 CIERA and Department of Physics & Astronomy, Northwestern University, 2145 Sheridan Rd., Evanston, IL 60208,USA

E-mail contact: gwolfchase at adlerplanetarium.org

We have discovered 12 new molecular hydrogen emission-line objects (MHOs) in the vicinity of the candidate massiveyoung stellar object Mol 121, in addition to five that were previously known. H2 2.12-µm/H2 2.25-µm flux ratiosindicate another region dominated by fluorescence from a photo-dissociation region (PDR), and one region thatdisplays an anomalously low H2 2.12-µm/H2 2.25-µm flux ratio (<1) and coincides with a previously reported deeplyembedded source (DES). Continuum observations at 3 mm reveal five dense cores; the brightest core is coincident withthe DES. The next brightest cores are both associated with cm continuum emission. One of these is coincident withthe IRAS source; the other lies at the centroid of a compact outflow defined by bipolar MHOs. The brighter of thesebipolar MHOs exhibits [Fe II] emission and both MHOs are associated with CH3OH maser emission observed at 95GHz and 44 GHz. Masses and column densities of all five cores are consistent with theoretical predictions for massivestar formation. Although it is impossible to associate all MHOs with driving sources in this region, it is evidentthat there are several outflows along different position angles, and some unambiguous associations can be made. Wediscuss implications of observed H2 2.12-µm/H2 2.25-µm and [Fe II] 1.64-µm/H2 2.12-µm flux ratios and compare theestimated total H2 luminosity with the bolometric luminosity of the region. We conclude that the outflows are drivenby massive young stellar objects embedded in cores that are likely to be in different evolutionary stages.

Accepted by The Astrophysical Journal

http://arxiv.org/pdf/1211.3440

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CO J = 2−1 and CO J = 3−2 observations toward the high-mass protostellar candidateIRAS 20188+3928

Jin-Long Xu1,2 and Jun-Jie Wang1,2

1 National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China2 NAOC-TU Joint Center for Astrophysics, Lhasa 850000, China

E-mail contact: xujl at bao.ac.cn

We have carried out 12CO J = 2 − 1 and 12CO J = 3 − 2 observations toward the high-mass protostellar candidateIRAS 20188+3928. Compared with previous observations, the 12CO J = 2 − 1 and 12CO J = 3 − 2 lines both haveasymmetric profiles with an absorption dip. The velocity of the absorption dip is 1.0 km s−1. The spectral shape maybe caused by rotation. The velocity-integrated intensity map and position-velocity diagram of the 12CO J = 2 − 1line present an obvious bipolar component, further verifying that this region has an outflow motion. This region isalso associated with an HII region, an IRAS source, and an H2O maser. The H2O maser has the velocity of 1.1 kms−1. Compared with the components of the outflow, we find that the H2O maser is not associated with the outflow.Using the large velocity gradient model, we concluded that possible averaged gas densities of the blueshifted lobe andredshifted lobe are 1.0 × 105 cm−3 and 2.0 × 104 cm−3, while kinetic temperatures are 26.9 K and 52.9 K, respectively.Additionally, the outflow has a higher integrated intensity ratio (ICO J=3−2/ICO J=2−1).

Accepted by Research in Astronomy and Astrophysics

http://arxiv.org/pdf/1211.3834

A mapping study of L1174 with 13CO J = 2 − 1 and 12CO J = 3 − 2: star formationtriggered by a Herbig Ae/Be star

Jing-Hua Yuan1, Yuefang Wu2, Jin Zeng Li1, Wentao Yu2, Martin Miller3

1 National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing100012, China2 Department of Astronomy, Peking University, 100871 Beijing, China3 I. Physikalisches Institut, Universitat zu Koln, Zulpicher Str. 77, 50937 Cologne, Germany

E-mail contact: ywu at pku.edu.cn

We have carried out a comprehensive study of the molecular conditions and star-forming activities in dark cloud L1174with multi-wavelength data. Mapping observations of L1174 in 13CO J = 2− 1 and 12CO J = 3− 2 were performedusing the KOSMA 3-meter telescope. Six molecular cores with masses ranging from 5 to 31 M⊙ and sizes rangingfrom 0.17 to 0.39 pc are resolved. Large area ahead of a Herbig Be star, HD 200775, is in expanding and core 1is with collapse signature. Large line widths of 13CO J = 2 − 1 indicate the ubiquity of turbulent motions in thisregion. Spectra of 12CO J = 3− 2 prevalently show conspicuously asymmetric double-peaked profiles. In a large area,red-skewed profiles are detected and suggestive of a scenario of global expansion. There is a large cavity around theHerbig Be star HD 200775, the brightest star in L1174. The gas around the cavity has been severely compressed bythe stellar winds from HD 200775. Feedbacks from HD 200775 may have helped form the molecular cores around thecavity. Seventeen 2MASS potential young stellar objects were identified according to their 2MASS colour indices. Thespatial distribution of the these 2MASS sources indicates that some of them have a triggered origin. All these suggestthat feedbacks from a Herbig Ae/Be star may also have the potential to trigger star forming activities.

Accepted for publication in MNRAS

http://arxiv.org/pdf/1211.1430

Orbital and Mass Ratio Evolution of Protobinaries Driven by Magnetic Braking

Bo Zhao and Zhi-Yun Li1

1 Dept. of Astronomy, University of Virginia, 530 McCormick Rd., Charlottesville, VA 22904, USA

E-mail contact: bz6g at virginia.edu

The majority of stars reside in multiple systems, especially binaries. The formation and early evolution of binaries is a

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longstanding problem in star formation that is not yet fully understood. In particular, how the magnetic field observedin star-forming cores shapes the binary characteristics remains relatively unexplored. We demonstrate numerically,using an MHD version of the ENZO AMR hydro code, that a magnetic field of the observed strength can drasticallychange two of the basic quantities that characterize a binary system: the orbital separation and mass ratio of thetwo components. Our calculations focus on the protostellar mass accretion phase, after a pair of stellar “seeds” havealready formed. We find that, in dense cores magnetized to a realistic level, the angular momentum of the materialaccreted by the protobinary is greatly reduced by magnetic braking. Accretion of strongly braked material shrinks theprotobinary separation by a large factor compared to the non-magnetic case. The magnetic braking also changes theevolution of the mass ratio of unequal-mass protobinaries by producing material of low specific angular momentumthat accretes preferentially onto the more massive primary star rather than the secondary. This is in contrast withthe preferential mass accretion onto the secondary previously found numerically for protobinaries accreting from anunmagnetized envelope, which tends to drive the mass ratio towards unity. In addition, the magnetic field greatlymodifies the morphology and dynamics of the protobinary accretion flow. It suppresses the traditional circumstellarand circumbinary disks that feed the protobinary in the non-magnetic case; the binary is fed instead by a fast collapsingpseudodisk whose rotation is strongly braked. The magnetic braking-driven inward migration of binaries from theirbirth locations may be constrained by high-resolution observations of the orbital distribution of deeply embeddedprotobinaries, especially with ALMA and JVLA.

Accepted by ApJ

http://arxiv.org/pdf/1210.2308

Abstracts of recently accepted major reviews

Our Astrochemical Heritage

Paola Caselli1 & Cecilia Ceccarelli2

1 School of Physics and Astronomy, Univ. of Leeds, Leeds LS2 9JT, UK2 Institut de Planetologie et d’Astrophysique de Grenoble, Grenoble, F-38041, France

E-mail contact: P.Caselli@leeds.ac.uk

Our Sun and planetary system were born about 4.5 billion years ago. How did this happen and what is our heritagefrom these early times? This review tries to address these questions from an astrochemical point of view. On the onehand, we have some crucial information from meteorites, comets and other small bodies of the Solar System. On theother hand, we have the results of studies on the formation process of Sun-like stars in our Galaxy. These results tellus that Sun-like stars form in dense regions of molecular clouds and that three major steps are involved before theplanet formation period. They are represented by the pre-stellar core, protostellar envelope and protoplanetary diskphases. Simultaneously with the evolution from one phase to the other, the chemical composition gains increasingcomplexity. In this review, we first present the information on the chemical composition of meteorites, comets andother small bodies of the Solar System, which is potentially linked to the first phases of the Solar System’s formation.Then we describe the observed chemical composition in the pre-stellar core, protostellar envelope and protoplanetarydisk phases, including the processes that lead to them. Finally, we draw together pieces from the different objects andphases to understand whether and how much we inherited chemically from the time of the Sun’s birth.

Accepted by The Astronomy and Astrophysics Review

http://arxiv.org/pdf/1210.6368

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The Dawn of Chemistry

Daniele Galli & Francesco Palla

INAF-Osservatorio Astrofisico di Arcetri Largo E. Fermi 5, 50125 Firenze, Italy

E-mail contact: galli@arcetri.astro.it

Within the precise cosmological framework provided by the Lambda-Cold Dark Matter model and standard Big Bangnucleosynthesis, the chemical evolution of the pregalactic gas can now be followed with accuracy limited only by theuncertainties on the reaction rates. Starting during the recombination era, the formation of the first molecules andmolecular ions containing hydrogen, deuterium, helium, and lithium was severely hindered by the low density of theexpanding universe, the intensity of the cosmic radiation field, and the absence of solid catalyzers. Molecular hydrogenand deuterated hydrogen, the most abundant species formed in the gas phase prior to structure formation, playeda fundamental role in the cooling of the gas clouds that gave birth to the first stellar generation, contributing todetermine the scale of fragmentation. Primordial molecules also interacted with the photons of the cosmic backgroundvia resonant scattering, absorption and emission. In this review we examine the current status of the chemistry ofthe early universe and discuss the most relevant reactions for which uncertainties still exist from theory or laboratoryexperiments. The prospects for detecting spectral distortions or spatial anisotropies due to the first atoms andmolecules are also addressed.

Accepted by Annual Review Astron. Astrophys.

http://arxiv.org/pdf/1211.3319

Evolution of Star Formation and Gas

Nick Z. Scoville1

1 Caltech, Pasadena, CA 91125, USA

E-mail contact: nzs at radio.caltech.edu

In these lectures I review observations of star-forming molecular clouds in our Galaxy and nearby galaxies to developa physical intuition for understanding star formation in the local and high-redshift Universe. A lot of this material isdrawn from early work in the field since much of the work was done two decades ago and this background is not generallyavailable in the present literature. I also attempt to synthesise our well-developed understanding of star formationin low-redshift galaxies with constraints from theory and observations at high redshift to develop an intuitive modelfor the evolution of galaxy mass and luminosity functions in the early Universe. The overall goal of this contributionis to provide students with background helpful for analysis of far-infrared (FIR) observations from Herschel andmillimetre/submillimetre (mm/submm) imaging with ALMA (the Atacama Large Millimetre/submillimetre Array).These two instruments will revolutionise our understanding of the interstellar medium (ISM) and associated starformation and galaxy evolution, both locally and in the distant Universe. To facilitate interpreting the FIR spectra ofGalactic star-forming regions and high-redshift sources, I develop a model for the dust heating and radiative transferin order to elucidate the observed infrared (IR) emissions. I do this because I am not aware of a similar coherentdiscussion in the literature.

Accepted by Cambridge University Press, Proceedings of the XXIII Canary Islands Winter School of Astrophysics”Secular Evolution of Galaxies”

http://arxiv.org/pdf/1210.6990

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Dissertation Abstracts

Instabilities in supersonic cloud–cloud collisions

Andrew McLeod

Thesis work conducted at: Cardiff University, United Kingdom

Current address: Astrophysics Group, University of Exeter, Stocker Road, EXETER, EX4 4QL, United Kingdom

Electronic mail: amcleod@astro.ex.ac.uk

Ph.D dissertation directed by: Prof Anthony Whitworth

Ph.D degree awarded: October 2012

We study the effects of the supersonic collision of molecular clouds using smoothed particle hydrodynamics (SPH)simulations. We review the observational evidence for cloud–cloud collision and previous computational work. Wedescribe the SPH method, the algorithms used in the SPH code SEREN (Hubber 2011), and how we have extendedthe parallelization of SEREN. We review the non-linear thin shell instability (NTSI) and gravitational instability in ashock-compressed layer.

We present the results of two sets of SPH simulations. In the first set of simulations we collide supersonic flows ofgas without self-gravity. We impose a range of velocity perturbations, including monochromatic perturbations, whitenoise perturbations and both subsonic and supersonic turbulence. The colliding flows create a dense shock-compressedlayer which is unstable to the NTSI.

We examine the effect of the differing initial perturbations on the NTSI, and calculate rates of growth of both bendingmodes and breathing modes as a function of time and wavenumber. We compare our results to the time-independentresult predicted by Vishniac (1994) for a one-dimensional monochromatic perturbation, and examine how this resultcan be extended to two-dimensional perturbations and non-monochromatic perturbations.

In our second set of simulations we model the head-on supersonic collision of two identical uniform-density spheres.We include self-gravity, allowing the dense layer to become gravitationally unstable and produce stars. We explorethe effect of increasing collision velocity, and show that the NTSI is present only at higher collision velocities. At thehighest collision velocities the NTSI severely disrupts the layer, and the collision does not produce stars. Althoughthe global properties of the collision, such as the thickness of the layer, the size of the star-forming region and thetime of first star formation, depend on the collision velocity, most individual properties of the stars do not.

Thesis available online at: http://orca.cf.ac.uk/38842/

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A comprehensive study of the young star cluster HD 97950 in NGC 3606

Xiaoying Pang

Heidelberg University

Key Lab for Astrophysics, Mbox 336 Room 301, Building 10, Shanghai Normal University, 100 Guilin Road,Shanghai 200234

Electronic mail: xiaoying0759 at gmail.com

Ph.D dissertation directed by: Prof. Dr. Eva Grebel

Ph.D degree awarded: May 2012

I study the young massive star cluster HD 97950 located in the Galactic giant H ii region NGC3603. My goals are(1) to estimate the survival probability of the cluster, (2) to investigate the origin of its mass segregation, and (3)to investigate the interplay between the cluster and the surrounding interstellar medium (ISM). All the studies aredone with data of the Hubble Space Telescope. I determine the cluster velocity dispersion from the stars’ relativeproper motions, and calculate the virial mass of the cluster. The cluster star formation efficiency is estimated to beabout 50%, which suggests that the HD97950 cluster will most likely survive as a bound cluster to gas expulsion. Iapply the Λ minimum spanning tree technique to measure the mass segregation down to 30M⊙. The high-mass starsare more segregated than low-mass stars, implying that the mass segregation in HD97950 is mostly of dynamicalorigin. To improve the age determination for the cluster stars that are severely reddened by the surrounding dustyISM, I compute a pixel-to-pixel distribution of the gas reddening, E(B − V )g, associated with the cluster. The radialprofiles of E(B−V )g show significant spatial variations around HD97950. Using UBV RI photometry, I estimate thestellar reddening of cluster stars. After correcting for foreground reddening, the total to selective extinction ratio inthe cluster is RV = 3.49± 0.79. The extinction curve in the UBV RI filters in the cluster is greyer than the averageGalactic extinction laws, but close to the extinction law for starburst galaxies. This indicates that stellar feedbackfrom massive stars changes the dust properties in the HD97950 cluster in a similar way as in starburst galaxies.

http://archiv.ub.uni-heidelberg.de/volltextserver/volltexte/2012/13399/

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New Jobs

Planetary Collisional Modeling

Arizona State University’s School of Earth and Space Exploration (SESE) is recruiting a Postgraduate Researcherin planetary collisional modeling, with an emphasis on early solar system bodies (e.g. planetary embryos, asteroids,comets, satellites, KBOs, ice giants). An earned PhD in Planetary Sciences, Astrophysics, Geophysics, ComputerModeling, or a related field is required. The successful applicant will have a demonstrated capability of using computermodels to tackle large-scale problems in astrophysics, geophysics, granular physics or fluid dynamics, and will havesome familiarity with the theory of hydrocodes, and a demonstrated ability to mine/reduce/visualize large quantitiesof 3D simulation data and analyze and clearly present the results. An academic track record in planet formation andevolution is desired but not required. The position is intended to bring a talented scholar to the forefront of thisexciting and expanding arena of research, working closely with Prof. Erik Asphaug and his colleagues and students.The successful applicant will lead at least one first-author paper per year, so a record of research publication isrequired. The position includes funding for travel to one domestic and one international conference per year, anddedicated access to the world-class computational facilities at ASU.

Applications are due by January 31, 2013 and reference letters by February 7, 2013 via email to exppd@asu.edu. Afull description of the application process is available at http://sese.asu.edu/opportunities. The appointment will starton or after March 1, 2013, and the position will remain open until filled. Salaries are competitive, and commensuratewith research experience. Students finishing their PhDs by July 2013 are encouraged to apply, as are applicants withpostgraduate experience looking for a new position. The initial appointment will be for 2 years.

ASU is an equal opportunity/affirmative action employer that actively seeks diversity among applicants and promotesa diverse workforce.

Florida Theoretical Astrophysics Postdoctoral Fellowship(s)

The University of Florida (UF) Department of Astronomy invites applications for one or more postdoctoral fellowshippositions in the Theoretical Astrophysics Group, with at least one appointment expected in the fields of star and/orplanet formation.

The anticipated start date is in Fall 2013. Successful candidate(s) will be expected to carry out original researchin theoretical astrophysics, independently and/or in collaboration with UF faculty in the Astronomy and/or Physicsdepartments. They will have access to the UF High Performance Computing Center, as well as observational facilities.

UF also has active observational and instrumentation groups. Candidates are encouraged to propose theoreticalresearch that relates to existing research programs and/or facilities at UF, including exoplanets, solar system studies,star and galaxy formation, and stellar populations. Further information, including a list of faculty and their researchinterests, is available at www.astro.ufl.edu.

The appointment is renewable annually for up to 3 years based on satisfactory performance, needs of the Departmentsand College, and available funding. A Ph.D. in a relevant field by the starting date is required. Application materials(CV, publications list, statement of research interests and plans (max 5 pages), and three letters of reference) shouldbe emailed to theory13@astro.ufl.edu. Application materials should be received by January 1, 2013 to ensure fullconsideration. For more information about the position, please contact Profs. Eric Ford, Anthony Gonzalez orJonathan Tan.

The University of Florida is an Equal Opportunity Institution.

Included Benefits: Successful candidates will be eligible for benefits, including health care plans.

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Postdoctoral Fellowship in Star and Planet Formation

The School of Physics and Astronomy at the University of Leeds invites applications for a postdoctoral fellowship in starand planet formation. The applicant is expected to work with Prof. Paola Caselli (and a team funded by the EuropeanResearch Council) to study star and planet formation, from the earliest phases of pre-stellar cores to the formation ofprotoplanetary disks. The overall aim of the project is to merge theoretical astrochemical, magneto-hydrodynamicaland radiative transfer models, and constrain them by detailed observations. Researchers with experience in star andplanet formation theory and/or observations are encouraged to apply.

Leeds has a very active research group in star and planet formation, also including Profs. Falle, Hartquist, Hoare,Oudmaijer and Drs. Lumsden and Pittard. Leeds has recently invested in a High Performance Computing (HPC)cluster (475 quad-core - i.e. 1900 cores - 2.8 GHz Intel Nehalem CPUs with 6 GB RAM per CPU). The University’smembership in the White Rose Grid and its status in a National Grid Node ensure continued cost effective and highquality support. The investment in infrastructure has also made it possible for Leeds to host one of the UKMHDclusters recently funded under the STFC HPC initiative, which will make around another 2000 cores available.

Salaries and duration of appointments (2+1 years, up to a maximum of 5 years) will be commensurate with expe-rience. Applications should consist of a CV, a brief description of past/current research and a list of publications.The application, as well as three letters of reference (sent directly by the referees), should be sent electronically top.caselli@leeds.ac.uk. Review of applications will begin on February 15th, 2013 and will continue until the position isfilled.

For more information, please send an email to Prof. P. Caselli (p.caselli@leeds.ac.uk).

Postdoctoral Position in Magnetism of Young Solar-type Stars

A 17-month post-doctoral position is available at IRAP (Institut de Recherche en Astrophysique et Planetologie,Toulouse University & CNRS, Toulouse, France), in the field of magnetism and activity of young solar-type stars. Theposition is supported by ANR (Agence Nationale de la Recherche).

The successful candidate will investigate the surface magnetism of cool open cluster stars and weak-line T Tauristars, using time-series collected with the ESPaDOnS and NARVAL stellar spectropolarimeters. The candidate willbe involved at all stages of this ongoing survey, from the preparation of future proposals to the acquisition, analysisand interpretation of data sets. The derived magnetic properties will be employed to study the evolution of dynamoprocesses and the related spindown of cool active stars, prior to the main sequence. The successful candidate will bein constant interaction with the teams of Toulouse (IRAP), Grenoble (IPAG), Saclay (CEA) and Montpellier (LUPM)involved in the observational and theoretical aspects of this project.

The ideal candidate is experienced in high-resolution spectroscopy and/or spectropolarimetry and has a background orexperience in high-level modeling of spectroscopic data, including multi-line analysis and tomographic imaging. Thecandidates, of any nationality, should have obtained by the starting date a Ph.D. in astronomy or a related field, withspecialization in one of the areas of study listed above. The start date of the appointment is flexible, but should beno later than March 2013. Candidates should submit a curriculum vitae, a summary of current and future researchinterests, a list of publications and two letters of recommendation to Pascal Petit (ppetit@irap.omp.eu) before 2012December 19.

Further information on the project can be found on the TOUPIES webpage:http://ipag.osug.fr/Anr_Toupies/spip.php?rubrique2

Postdoc Position in Star Formation at CEA Saclay

We invite applications to fill two postdoctoral research positions in the Astrophysical Group (SAp) at CEA/Saclay inthe context of the MAGMIST project, a five-year founded program of the European Research Council (ERC). It is

55

centered on a detailed investigation of the star formation process from galactic to molecular core scales using mainlythree dimensional numerical simulations, analytical modeling and confrontation with observations.

The successful candidates should have an experience in at least one of the following topics: large numerical simulations,fluid dynamics, star formation or interstellar medium.

The project offers competitive salaries and money for traveling. All positions are for four years and include full benefit.The CEA/Saclay group has extensive expertize in heavy computation and easy access to local and national computingfacilities and hosts both observers and theorists.

Required application materials include a CV, a bibliography, a statement of research interests and three letters ofrecommendation and should be send by regular mail or email to :

Dr Patrick HennebelleSAp - CEA/Saclay91191 Gif-sur-YvetteFrance

Moving ... ??

If you move or your e-mail address changes, pleasesend the editor your new address. If the Newsletterbounces back from an address for three consecutivemonths, the address is deleted from the mailing list.

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Meetings of Possible Interest

Exoplanets in Multi-body Systems in the Kepler Era

9 - 16 February 2013 Aspen, CO, USAhttp://www.astro.ufl.edu/~eford/meetings/aspen2013/

Characterising Exoplanets: Detection, Formation, Interiors, Atmospheres and Habitability

11 - 12 March 2013 The Royal Society, London, UKhttp://royalsociety.org/events/2013/exoplanets/

43nd Saas-Fee Course: Star Formation in Galaxy Evolution: Connecting Numerical Models to Reality

11 - 16 March 2013 Villars-sur-Ollon, Switzerlandhttp://lastro.epfl.ch/conferences/sf2013

Infrared and Submillimeter Probes of Gas in Galaxies: From the Milky Way to the Distant Universe

17 - 20 March 2013 Pasadena, CA USAhttp://conference.ipac.caltech.edu/gasconf/

From Stars to Life - Connecting our Understanding of Star Formation, Planet Formation, Astrochem-

istry and Astrobiology

3 - 6 April 2013 Gainesville, Florida, USAhttp://conference.astro.ufl.edu/STARSTOLIFE/

StarBench: A Workshop for the Benchmarking of Star Formation Codes

8 - 11 April 2013 University of Exeter, UKhttp://www.astro.ex.ac.uk/people/haworth/workshop_bench/index.html

Transformational Science with ALMA: From Dust to Rocks to Planets - Formation and Evolution of

Planetary Systems

8 - 12 April 2013 Hilton Waikoloa Village, The Big Island of Hawaii, USAhttp://www.cv.nrao.edu/rocks/index.html

International Young Astronomer School on Exploiting the Herschel and Planck data

15 - 19 April 2013 Meudon, Francehttp://ufe.obspm.fr/rubrique344.html

Habitable Worlds Across Time and Space

29 April - 2 May 2013 Space Telescope Science Institute, Baltimore, USAhttp://www.stsci.edu/institute/conference/habitable-worlds

Ice and Planet Formation

15 - 17 May 2013 Lund Observatory, Swedenhttp://www.astro.lu.se/~anders/IPF2013/

IAU Symposium 297: The Diffuse Interstellar Bands

20 - 24 May 2013 Noordwijkerhout, The Netherlandshttp://iau297.nl/

Brown Dwarfs come of Age

20 - 24 May 2013 Fuerteventura, Canary Islands, Spainno web site yet

The Origins of Stellar Clustering - from Fragmenting Clouds to the Build-up of Galaxies

26 May 2013 - 16 June 2013 Aspen, Colorado, USAhttp://www.mpa-garching.mpg.de/~diederik/aspen2013

57

IAU Symposium 299: Exploring the Formation and Evolution of Planetary Systems

2 - 7 June 2013 Victoria, BC, Canadahttp://www.iaus299.org

Massive Stars: From alpha to Omega

10 - 14 June 2013 Rhodes, Greecehttp://a2omega.astro.noa.gr

Lin-Shu Symposium: Celebrating the 50th Anniversary of the Density-Wave Theory

24 - 28 June 2013 Beijing, Chinano web site yet

Protostars and Planets VI

15 - 20 July 2013 Heidelberg, Germanyhttp://www.ppvi.org

Dust Growth in Star & Planet Formation 2013

22 - 25 July 2013 MPIA, Heidelberg, Germanyno web site yet

2013 Sagan Summer Workshop: Imaging Planets and Disks

29 July - 2 August 2013 Pasadena, CA, USAhttp://nexsci.caltech.edu/workshop/2013/

IAUS 302 - Magnetic Fields Throughout Stellar Evolution

26 - 30 August 2013 Biarritz, Francehttp://iaus302.sciencesconf.org

Meteoroids 2013. An International Conference on Minor Bodies in the Solar System

26 - 30 August 2013 Dep. of Physics, A.M. University, Poznan, Polandhttp://www.astro.amu.edu.pl/Meteoroids2013/index.php

Exoplanets and Brown Dwarfs

2 - 5 September 2013 de Havilland, University of Hertfordshire, Hatfield, Nr. London, UKno web site yet

The Life Cycle of Dust in the Universe: Observations, Theory, and Laboratory Experiments

18 - 22 November 2013 Taipei, Taiwanhttp://events.asiaa.sinica.edu.tw/meeting/20131118/

The 18th Cambridge Workshop on Cool Stars, Stellar Systems and the Sun

9 - 13 June 2014 Flagstaff, Arizona, USAhttp://www2.lowell.edu/workshops/coolstars18/

Living Together: Planets, Stellar Binaries and Stars with Planets

8 - 12 September 2014 Litomysl Castle, Litomysl, Czech Republicno web site yet

Towards Other Earths II. The Star-Planet Connection

15 - 19 September 2014 Portugalhttp://www.astro.up.pt/toe2014

Other meetings: http://www1.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/meetings/

58

New Books

The Formation and Early Evolution of Stars

Norbert S. Schulz

This is the second, revised edition of the book “From Dust to Stars” (presented in SFNL #154) that appeared in2005. The major and rapid progress in our field has required significant updates to the text. Three chapters, onmultiplicity in young stellar objects, on massive star formation, and on exoplanets and planet formation, have beenadded, resulting in this new, expanded book. References are given to the key literature throughout the text, anda reference list at the end of the book contains more than 1300 entries, the majority of which date to the past 10years. Although not written specifically as a text book for a course on star formation, this comprehensive and easilyaccessible text will appeal to both undergraduate and graduate students, as well as researchers who wish to get anoverview of the current state of star formation studies.

The following lists the chapters and subsections of the book:

1 About the Book

2 Historical Background

2.1 And There Was Light?2.2 The Quest to Understand the Formation of Stars2.3 Observing Stellar Formation

3 Studies of Interstellar Matter

3.1 The Interstellar Medium3.2 Interstellar Gas3.3 Column Densities in the ISM3.4 Interstellar Dust3.5 The ISM in other Galaxies

4 Molecular Clouds and Cores

4.1 Global Cloud Properties4.2 Clud Dynamics4.3 Dynamic Properties of Cores

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5. Concepts of Stellar Collapse

5.1 Classical Collapse Concepts5.2 Stability Considerations5.3 Collapse of Rotating and Magnetized Clouds5.4 Cores, Disks and Outflows: the Full Solution?

6 Evolution of Young Stellar Objects

6.1 Protostellar Evolution6.2 Evolution in the HR-Diagram6.3 PMS Classifications

7 Multiplicity in Star Formation

7.1 Observational Account7.2 PMS Properties of Binaries7.3 Formation of Binaries7.4 Mass Transfer in Compact Binaries

8 Accretion Phenomena and Magnetic Activity in YSOs

8.1 Accretion Disks8.2 Stellar Rotation in YSOs8.3 Magnetic Activity in PMS Stars

9 Massive Star Formation

9.1 Properties of Young Massive Stars9.2 Distribution of Massive Stars9.3 Observations of Eary Stages9.4 Formation Concepts9.5 Multiplicity9.6 The First Stars

10 High-energy Signatures in YSOs

10.1 The X-ray Account of YSOs10.2 X-rays from Protostars10.3 X-ray Spectra of PMS Stars10.4 γ-Radiation from YSOSs

11 Star-Forming Regions

11.1 Embedded Stellar Clusters11.2 Well-studied Star-forming Regions11.3 Formation on Large Scales

12 Proto-solar Systems and the Sun

12.1 Protoplanetary Disks12.2 The Making of the Sun

13 Protoplanets and Exoplanets

13.1 The Search for Exoplanets13.2 The Search for Protoplanets13.3 Planet Formation

Appendix A Gas Dynamics

Appendix B Magnetic Fields and Plasmas

Appendix C Radiative Interactions with Matter

Appendix D Spectroscopy

Springer 2012, ISBN 978-3-642-23925-0515 pages, hardcover US$119.00Available from http://www.springer.com/astronomy/book/978-3-642-23925-0

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Short Announcements

American Chemical Society (ACS) Creates New AstrochemistrySubdivision

At the national ACS meeting in Philadelphia, the ACS-PHYS division established a new Astrochemistry Subdivision.Astrochemistry is the study of the abundances and chemical reactions of atoms, molecules, and ions and how theyinteract with radiation in both gas and condensed phases in Solar Systems and in the Interstellar Medium. The newSubdivision provides an interdisciplinary ”home” for individuals interested in this growing research area.

We would like to invite you and the undergraduate students, graduate students, and postdoctoral fellows in yourgroup to join the ACS Astrochemistry Subdivision to connect to an exciting research endeavor and to further promotethe Astrochemistry Subdivision at (international) meetings, in your university, and in your department. Additionalinformation on joining the Subdivision may be found at:

http://www.chem.hawaii.edu/Bil301/ACSAstrochemistry.html

An inaugural Astrochemistry Symposium will be held at the Fall ACS National Meeting in Indianapolis, IN, September8-12, 2013. Please also email us (ralfk@hawaii.edu, asuits@chem.wayne.edu,mhg@cchem.berkeley.edu) suggestions forforthcoming ACS Astrochemistry Symposia and nominations for officers for the Astrochemistry subdivision.

We would also like to thank those of you who supported the establishment of the Astrochemistry Subdivision! Wehope that the new Subdivision will effectively serve this thriving scientific community.

Best regards,

Ralf Kaiser (Chair), Arthur Suits (Chair-Elect), Martin Head-Gordon (Vice-Chair)

50 Years of Brown Dwarfs:from Theoretical Prediction to Astrophysical Studies

Talks and posters of this Ringberg conference (Oct. 2012) are now online:http://www.mpia.de/homes/joergens/ringberg2012_proc.html

The talks and posters presented at this international conference at Ringberg Castle on Oct 21-24, 2012 summarizethe historical aspects concerning the 50th anniversary of the theoretical prediction of brown dwarfs (S. Kumar) andof first brown dwarf discoveries (e.g., B. Oppenheimer, R. Rebolo, G. Basri). Furthermore, various aspects of browndwarf research were presented, including the physics of brown dwarfs (I. Baraffe) and the properties of young (e.g.,M. Zapatero-Osorio, K. Luhman) and ultracool L, T, and Y dwarfs (M. Cushing). A focus of the workshop was theexploration of the origin of brown dwarfs in context with brown dwarf binaries. Presentations on observational binarystudies (RV and direct imaging, e.g., B. Biller, C. Blake, and T. Dupuy) met with theories in the field of brown dwarfformation (e.g., S. Basu, M. Bate, P. Clark, S. Inutsuka) in a very fruitful atmosphere. Most of the talks and postersare now online.

SOC: Viki Joergens, Thomas Henning, Isabelle Baraffe, Gibor Basri, Wolfgang Brandner, Adam Burgasser, CathieClarke, Ralf Klessen, Keivan Stassun

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