Ongoing Extragalactic HI Surveys at Arecibo: the Local HI UniverseRiccardo Giovanelli (Cornell University) Washington, DC, Sep07

ALFALFA: 7000 sq.deg., 48 sec/beam, 2 mJy/bm (P.I.: R. Giovanelli, Cornell, U.S.)Fully blind survey, expected N>20,000 detAGES: 300 sq.deg., 300s/beam (P.I.: J. Davies, Cardiff, UK) selected fields, expected N (scaling law)~1350 but v likely higherAUDS: 0.36 sq.deg., 50 hrs/bm, 50 mJy/bm (P.I.: W. Freudling, ESO, Germany)Fully blind survey, expected N ~ 102 det at z~0.1 ZOA: ~200 sq.deg.(?) Commensal with G-ALFA/P-ALFA surveys (P.I.: P. Henning, New Mexico, U.S.)Fully blind survey, Zone of Avoidance, expected N ~ 500(?)NGC2903: small area map on nearby galaxy; not a LS survey (P.I.: J. Irwin, Queens U., Canada)Ongoing Extragalactic HI Surveys at AO

1 Determination & environmental variation of the faint end of the HI Mass Function and the cosmic abundance of low mass halos

2 Global properties of HI-selected galaxy samples

3 The LSS of HI sources, the void problem & metallicity

4 Blind Survey for HI tidal remnants & cold accretion

5 HI Diameter Function

6 The low HI Column density environment of galaxies

7 The nature of HVCs around the MW (and beyond?)

8 HI absorbers and the link to Lyman a absorbers

9 OH Megamasers at intermediate redshift

10 Evolution of the HI Mass Function

11 Map local LSS in optically obscured regions

Parkes HIPASS survey: Zwaan et al. 2003?The HI Mass Function (HIMF)Previous surveys have detected few (if any) objects with low HI.At low mass end, HIMF estimates differ by >10X:Rosenberg & Schneider (2000) versusZwaan et al. (1997)

Numerical simulations predict the existence of lots of low mass halos, but so far, we have not found very many of them.

Do they exist?Are baryons in small Dark Matter halos fried at the epoch of reionization?Are they blown away by the first generation of stars?Are they retained but unable to make stars?Is that more likely in cosmic voids?

Leo TSlide credit: T. Oosterloo

Leo TSlide credit: T. OosterlooMHI = 3x105 solarMHI/LV = 5MHI/Mbaryon = 0.8

The minimun integration time in sec , to detect an HI mass MHI at the distance DMpc with ALFA@Arecibo, isi.e. the Depth of the survey increases only as AlternativelyDetection of an HI mass 109 solar, W=200 km/s at z=0.1 will require about 6 hrs(*)(*)Reality CheckBut dont despair: HI has been detected at AO at z=0.28 (Catinella et al. 2007)

Over the ~1000 sq. deg. including the northern part of Virgo :

ALFALFA detects 5200 sources, HIPASS 178 (several unconfirmed)While this region is perhaps the most intensively studied in the local Universe, at all wavelength bands (including HI, using optically selected samples), 69% of ALFALFA detections are new (the conventional wisdom on which optical targets would turn out to be HI-rich appears to have been limited)

HIPASS Completeness Limit HIPASS Limit

Source extraction and identification of counterparts at other wavelength regimes can be a painful experience...source centroiding as accurately as possible is thus highly desirable

Suppose HIPASS detects a source at S/N~6 near 3000 km/s in this field. The position error box will have a radius of ~2.5.The opt counterpart could be gal #1, 2, 3, 4, 5 or 6.ALFALFA will detect the same source with S/N~50Centroiding accuracy goes roughly as

HPFW(PSF)/(S/N)and the Arecibo beam is as wide as the Parkes one The same source will have an ALFALFA position error of ~ 0.1123456

AGES

B. Kent Ph.D. Thesis

ALFALFA: B. Kent Ph.D. Thesis

B. Kent Ph.D. Thesis

B. Kent Ph.D. Thesis

B. Kent Ph.D. Thesis Brown: XrayPurple: OptBlue: HI

Haynes, Giovanelli & Kent 2007, ApJL

v: 1915-1945v: 1852-1883v: 1821-1852v: 1883-1915Koopmann et al. in prep.NGC4532DDO137Hoffman et al 1999

Slide credit: J. X. Prochaska 2007

An extragalactic spectral line survey To cover 7000 sq deg of high galactic latitude sky1345-1435 MHz (-2000 to +17500 km/s for HI line) 5 km/s resolution 2-pass, drift mode (total int. time per beam ~ 40 sec) ~2 mJy rms [MHI~105 in LG, ~107 at Virgo distance] 4000 hrs of telescope time, 6-7 years started Feb 2005; as of Feb 2007, 1/3 completeOne of several major surveys currently ongoing at Arecibo, exploiting its multibeam capabilityhttp://egg.astro.cornell.edu/alfalfaALFALFA, a Legacy Survey

Who is ALFALFA?ALFALFA is an open collaboration: anybody with a valid scientific interest can join.

For participation guidelines, see: http://egg.astro.cornell.edu/alfalfa/joining.php

Recommended guidelines for authorship can be found at:http://egg.astro.cornell.edu/alfalfa/projects/authorshipguidelines.php

Project Guidelines: http://egg.astro.cornell.edu/alfalfa/projects/projectguidelines.phpProjects (Team/PhD/undergrad): http://egg.astro.cornell.edu/alfalfa/projects/projects.php

ALFALFA data products can be accessed through the web using robust, NVO-compatible software tools, developed by our students, thanks to an NSF/NVO development grant and the archival support of the Cornell Theory Center.ALFALFA is already an integral part of the NVO footprinthttp://arecibo.tc.cornell.edu/hiarchive/alfalfa/

Science Goals to Be Addressed by ALFALFA:1 Determination & environmental variation of the faint end of the HI Mass Function and the cosmic abundance of low mass halos

2 Global properties of HI-selected galaxy samples

3 The LSS of HI sources, the void problem & metallicity

4 Blind Survey for HI tidal remnants & cold accretion

5 HI Diameter Function

6 The low HI Column density environment of galaxies

7 The nature of HVCs around the MW (and beyond?)

8 HI absorbers and the link to Lyman a absorbers

9 OH Megamasers at intermediate redshift

ALFALFA: Preliminary Results from 2 strips through VirgoRA: 07:40h to 16:30hDec: 12deg to 16deg and 08deg to 12degSolid Angle: 1028 sq deg (15% of survey)

A quick look at the Virgo Cluster

B. Kent Ph.D. Thesis

What about dark galaxies?

No optical counterpartEvidence of rotation: Vrot~13 km/sMHI=6x108 solarMdyn(

The Cardiff Dark Galaxy VirgoHI-21

10NGC 425445 kpcDSS2 Blue

Minchin et al 2007 (WSRT)

Combined ALFALFA data around NGC 4254 cz = 2243 to 2557 km/s1045 kpcHaynes, Giovanelli & Kent (2007 ApJL submitted)MHI = 5x109 solar

1045 kpcCombined ALFALFA data around VIRGOHI21 cz = 1946 to 2259 km/sHaynes, Giovanelli & Kent (2007 ApJL)Stream MHI = 5x108 solarMinchin et al 2007 (WSRT)

Note the following:The prominent, anomalous m=1 spiral structure of N4254 is visible in the gas and in the old stellar pop: gravity at workThe HI mass in the stream is only 10% of HI mass in N4254: albeit spectacular, disturbance of NGC 4254 is relatively mildVelocity field of the stream shows the coupling of the tidal force and rotation of NGC 4254, suggesting an interesting timing argument:The stream exhibits memory of a full rotational cycleFrom the VLA map of N4254, we get the outer HI radius and Vrot at that radius rotation period ~ 800 MyrHence the duration of the tidal encounter ~800 Myr, comparable with the cluster crossing time were witnessing an event of mild harassment of NGC 4254 in its high velocity transit through the periphery of the cluster

Duc : simulation ALFALFA: dataCredit: Duc & Bournaud 2007

Haynes, Giovanelli & Kent 2007, ApJLDucs simulationP-V diagram

Does a cosmologically important population of optically faint but baryon rich low mass halos exist?

Do such objects preferentially exist in regions of low cosmic density (voids), in which massive galaxies are known to be underrepresented?

Does a significant population of optically dark galaxies exist?

If they exist, are such objects primordial or the result of secular processes?

Is there a cosmic density dependence of metallicity, i.e. do low mass systems in voids have preferentially lower heavy element abundances?ALFALFA as a low z HI Cosmology Survey

Does a cosmologically important population of optically faint but baryon rich low mass halos exist?

Do such objects preferentially exist in regions of low cosmic density (voids), in which massive galaxies are known to be underrepresented?

Does a significant population of optically dark galaxies exist?

If they exist, are such objects primordial or the result of secular processes?

Is there a cosmic density dependence of metallicity, i.e. do low mass systems in voids have preferentially lower heavy element abundances?ALFALFA as a low z HI Cosmology Surveyyesno; Saintonge 2007 PhD thesis; Haynes talkOptically inert objects detected; see Kent et al. 2007 ApJLthe latter; Haynes et al. 2007 ApJLProb no; Saintonge 2007(Basilakos et al 2007)

http://egg.astro.cornell.edu/alfalfaFor participation guidelines, see: http://egg.astro.cornell.edu/alfalfa/joining.phphttp://arecibo.tc.cornell.edu/hiarchive/alfalfa/Catalog access at: