Ongoing Extragalactic HI Surveys Ongoing Extragalactic HI Surveys at Arecibo:at Arecibo:

the Local HI Universethe Local HI Universe

Riccardo Giovanelli Riccardo Giovanelli (Cornell University)(Cornell University)

Washington, DC, Sep07Washington, DC, Sep07

•ALFALFAALFALFA: 7000 sq.deg., 48 sec/beam, 2 mJy/bm (P.I.: R. Giovanelli, Cornell, U.S.)

Fully blind survey, expected N>20,000 det

•AGESAGES: 300 sq.deg., 300s/beam (P.I.: J. Davies, Cardiff, UK) selected fields, expected N (scaling law)~1350 – but v likely higher

•AUDS:AUDS: 0.36 sq.deg., 50 hrs/bm, 50 Jy/bm (P.I.: W. Freudling, ESO, Germany)

Fully blind survey, expected N ~ 102 det at z~0.1

•ZOA: 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:NGC2903: small area map on nearby galaxy; not a LS survey (P.I.: J. Irwin, Queens U., Canada)

Ongoing Extragalactic HI Surveys at AOOngoing 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 HVC’s around the MW (and beyond?)

8 HI absorbers and the link to Lyman 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)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)

versus

Zwaan 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 TLeo T

Slide credit: T. Oosterloo

Leo TLeo T

Slide credit: T. Oosterloo

MHI = 3x105 solar

MHI/LV = 5

MHI/Mbaryon = 0.8

2/34

2

6 1001025.0

kmsMpc

sun

HIs

WD

M

Mt

The minimun integration time in sec , to detect an HI mass MHI at the distance DMpc with ALFA@Arecibo, is

i.e. the Depth of the survey increases only as

4/1sMpc tD

Alternatively

4/322/1

7 257.16sec1002.1

10

kmsMpcs

sun

HI WDt

M

M

Detection of an HI mass 109 solar, W=200 km/s at z=0.1 will require about 6 hrs

(*)

(*)

Reality Check

But don’t 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 :Over the ~1000 sq. deg. including the northern part of Virgo :

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

HIPASS Completeness LimitHIPASS Completeness Limit

HIPASS LimitHIPASS Limit

Source extraction and Source extraction and identification of identification of counterparts at other counterparts at other wavelength regimes can be wavelength regimes can be a painful experience…a painful experience…

...source centroiding as ...source centroiding as accurately as possible is accurately as possible is thus highly desirablethus highly desirable

Suppose HIPASS detects a source Suppose HIPASS detects a source at S/N~6 near 3000 km/s in this at S/N~6 near 3000 km/s in this field. The position error box will field. The position error box will have a radius of ~2.5’.have a radius of ~2.5’.

The opt counterpart could be gal The opt counterpart could be gal #1, 2, 3, 4, 5 or 6.#1, 2, 3, 4, 5 or 6.

ALFALFA will detect the same ALFALFA will detect the same source with S/N~50source with S/N~50

Centroiding accuracy goes Centroiding accuracy goes roughly as roughly as

HPFW(PSF)/(S/N)HPFW(PSF)/(S/N)

and the Arecibo beam is ¼ as and the Arecibo beam is ¼ as wide as the Parkes onewide as the Parkes one

The same source will have The same source will have an ALFALFA position erroran ALFALFA position error of ~ 0.1’of ~ 0.1’

11

22

33

44

55

66

AGESAGES

B. Kent Ph.D. Thesis B. Kent Ph.D. Thesis

ALFALFA: 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 B. Kent Ph.D. Thesis

B. Kent Ph.D. Thesis B. Kent Ph.D. Thesis

Brown: XrayBrown: XrayPurple: OptPurple: OptBlue: HIBlue: HI

Haynes, Giovanelli & Kent 2007, ApJL Haynes, Giovanelli & Kent 2007, ApJL

v: 1915-1945v: 1915-1945

v: 1852-1883v: 1852-1883 v: 1821-1852v: 1821-1852

v: 1883-1915v: 1883-1915

Koopmann et al. in prep.

NGC4532

DDO137

Hoffman et al 1999

Slide credit: J. X. Prochaska 2007

• An extragalactic spectral line survey • To cover 7000 sq deg of high galactic latitude sky• 1345-1435 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 complete

• One of several major surveys currently ongoing at Arecibo, exploiting its multibeam capability

http://http://egg.astro.cornell.edu/alfalfaegg.astro.cornell.edu/alfalfa

ALFALFA,ALFALFA, a Legacy a Legacy SurveySurvey

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.php

Projects (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 footprint

http://arecibo.tc.cornell.edu/hiarchive/alfalfa/

Science Goals to Be Addressed by 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 HVC’s around the MW (and beyond?)

8 HI absorbers and the link to Lyman absorbers

9 OH Megamasers at intermediate redshift

ALFALFA: Preliminary Results ALFALFA: Preliminary Results from 2 strips through Virgofrom 2 strips through Virgo

RA: 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 ClusterA quick look at the Virgo Cluster

B. Kent Ph.D. Thesis B. Kent Ph.D. Thesis

What about “dark galaxies”?What about “dark galaxies”?

-No optical counterpartNo optical counterpart

-Evidence of rotation: VEvidence of rotation: Vrotrot~13 km/s~13 km/s

-MMHIHI=6x10=6x1088 solar solar

-MMdyndyn(<3’)~7x10(<3’)~7x1088 solar solar

Giovanelli & Haynes 1989 ApJ 346, L5 : Arecibo discoveryGiovanelli & Haynes 1989 ApJ 346, L5 : Arecibo discovery

Chengalur, Giovanelli & Haynes 1995 AJ 109, 2415: VLA mapChengalur, Giovanelli & Haynes 1995 AJ 109, 2415: VLA map

HI 1225+01HI 1225+01

MMHIHI = 2x10 = 2x1099 solar solar

MMdyndyn~7x10~7x1099 solar solar

SF opt counterpartSF opt counterpart

But do such But do such objects exist objects exist in isolation?in isolation?

The Cardiff “Dark Galaxy”The Cardiff “Dark Galaxy” VirgoHI-21VirgoHI-21

10’NGC 4254

45 kpcDSS2 Blue

Minchin et al 2007 (WSRT)

Combined ALFALFA data around NGC 4254 cz = 2243 to 2557 km/s

10’

45 kpcHaynes, Giovanelli & Kent (2007 ApJL submitted)Haynes, Giovanelli & Kent (2007 ApJL submitted)

MMHIHI = 5x10 = 5x1099 solar solar

10’

45 kpc

Combined ALFALFA data around VIRGOHI21 cz = 1946 to 2259 km/s

Haynes, Giovanelli & Kent (2007 ApJL)Haynes, Giovanelli & Kent (2007 ApJL)

Stream MStream MHIHI = 5x10 = 5x1088 solar solarMinchin et al 2007 (WSRT)

Note the following:Note the following:

•The prominent, anomalous m=1 spiral structure of N4254 is The prominent, anomalous m=1 spiral structure of N4254 is visible in the gas and in the old stellar pop: visible in the gas and in the old stellar pop: gravity at workgravity at work

•The HI mass in the stream is only 10% of HI mass in N4254: The HI mass in the stream is only 10% of HI mass in N4254: albeit spectacular, disturbance of NGC 4254 is relatively mildalbeit spectacular, disturbance of NGC 4254 is relatively mild

•Velocity field of the stream shows the coupling of the tidal Velocity field of the stream shows the coupling of the tidal force and rotation of NGC 4254, suggesting an interesting force and rotation of NGC 4254, suggesting an interesting timing argument:timing argument:

•The stream exhibits memory of a full rotational cycleThe stream exhibits memory of a full rotational cycle

•From the VLA map of N4254, we get the outer HI radius and From the VLA map of N4254, we get the outer HI radius and Vrot at that radius Vrot at that radius rotation period ~ 800 Myr rotation period ~ 800 Myr

•Hence the duration of the tidal encounter Hence the duration of the tidal encounter

~800 Myr, comparable with the cluster crossing time~800 Myr, comparable with the cluster crossing time

we’re witnessing an event of mild harassment of NGC 4254 we’re witnessing an event of mild harassment of NGC 4254 in its high velocity transit through the periphery of the clusterin its high velocity transit through the periphery of the cluster

Duc : simulation ALFALFA: dataDuc : simulation ALFALFA: dataCredit: Duc & Bournaud 2007Credit: Duc & Bournaud 2007

Haynes, Giovanelli & Kent 2007, ApJLHaynes, Giovanelli & Kent 2007, ApJL

Duc’s simulationDuc’s simulationP-V diagramP-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 Survey

yesyes

no; Saintonge 2007 PhD thesis; Haynes’ talkno; Saintonge 2007 PhD thesis; Haynes’ talk

Optically inert objects detected; see Kent et al. 2007 ApJLOptically inert objects detected; see Kent et al. 2007 ApJL

the latter; Haynes et al. 2007 ApJLthe latter; Haynes et al. 2007 ApJL

Prob no; Saintonge 2007Prob no; Saintonge 2007

(Basilakos et al 2007)(Basilakos et al 2007)

http://http://egg.astro.cornell.edu/alfalfaegg.astro.cornell.edu/alfalfa

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

http://arecibo.tc.cornell.edu/hiarchive/alfalfa/

Catalog access at:Catalog access at: