Ongoing Extragalactic HI Surveys at Arecibo: the Local HI Universe the Local HI Universe Riccardo Giovanelli (Cornell University) Washington, 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 ~ 10 2 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 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 ? 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 T Slide credit: T. Oosterloo

Leo T Slide credit: T. Oosterloo M HI = 3x10 5 solar M HI /L V = 5 M HI /M baryon = 0.8

The minimun integration time in sec, to detect an HI mass M HI at the distance D Mpc with is i.e. the Depth of the survey increases only as Alternatively Detection of an HI mass 10 9 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 :  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 in the local Universe, at all wavelength bands (including HI, using optically selected samples), HI, using optically selected samples),  69% of ALFALFA detections are new (the conventional  69% of ALFALFA detections are new (the conventional wisdom on which optical targets would turn out to be wisdom 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 Limit HIPASS 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~50 Centroiding accuracy goes roughly as HPFW(PSF)/(S/N) HPFW(PSF)/(S/N) and the Arecibo beam is ¼ as wide as the Parkes one  The same source will have an ALFALFA position error an ALFALFA position error of ~ 0.1’ of ~ 0.1’

AGES

B. Kent Ph.D. Thesis

ALFALFA: B. Kent Ph.D. Thesis

B. Kent Ph.D. Thesis

Brown: Xray Purple: Opt Blue: HI

Haynes, Giovanelli & Kent 2007, ApJL

v: v: v: v: 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 MHz (-2000 to km/s for HI line) 5 km/s resolution 2-pass, drift mode (total int. time per beam ~ 40 sec) ~2 mJy rms [M HI ~10 5 in LG, ~10 7 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 falfa ALFALFA, a Legacy Survey

Who is ALFALFA? ALFALFA is an open collaboration: anybody with a valid scientific interest can join. For participation guidelines, see: Recommended guidelines for authorship can be found at: Project Guidelines: Projects (Team/PhD/undergrad):

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

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 from 2 strips through Virgo from 2 strips through Virgo RA: 07:40h to 16:30h Dec: 12deg to 16deg and 08deg to 12deg Solid 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 counterpart -Evidence of rotation: V rot ~13 km/s -M HI =6x10 8 solar -M dyn (<3’)~7x10 8 solar Giovanelli & Haynes 1989 ApJ 346, L5 : Arecibo discovery Chengalur, Giovanelli & Haynes 1995 AJ 109, 2415: VLA map HI M HI = 2x10 9 solar M dyn ~7x10 9 solar SF opt counterpart But do such objects exist in isolation?

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

10’ NGC kpc DSS2 Blue

Minchin et al 2007 (WSRT)

Combined ALFALFA data around NGC 4254 cz = 2243 to 2557 km/s 10’ 45 kpc Haynes, Giovanelli & Kent (2007 ApJL submitted) M HI = 5x10 9 solar

10’ 45 kpc Combined ALFALFA data around VIRGOHI21 cz = 1946 to 2259 km/s Haynes, Giovanelli & Kent (2007 ApJL) Stream M HI = 5x10 8 solar Minchin et al 2007 (WSRT)

Note the following: 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 prominent, anomalous m=1 spiral structure of N4254 is visible in the gas and in the old stellar pop: gravity at work The HI mass in the stream is only 10% of HI mass in N4254: albeit spectacular, disturbance of NGC 4254 is relatively mildThe HI mass in the stream is only 10% of HI mass in N4254: albeit spectacular, disturbance of NGC 4254 is relatively mild Velocity field of the stream shows the coupling of the tidal force and rotation of NGC 4254, suggesting an interesting timing argument:Velocity 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 cycleThe stream exhibits memory of a full rotational cycle From the VLA map of N4254, we get the outer HI radius and Vrot at that radius  rotation period ~ 800 MyrFrom the VLA map of N4254, we get the outer HI radius and Vrot at that radius  rotation period ~ 800 Myr Hence the duration of the tidal encounterHence 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 in its high velocity transit through the periphery of the cluster

Duc : simulation ALFALFA: data Credit: Duc & Bournaud 2007

Haynes, Giovanelli & Kent 2007, ApJL Duc’s simulation P-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 yes no; Saintonge 2007 PhD thesis; Haynes’ talk Optically inert objects detected; see Kent et al ApJL the latter; Haynes et al ApJL Prob no; Saintonge 2007 (Basilakos et al 2007)

falfa For participation guidelines, see: Catalog access at: