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Ongoing Extragalactic HI Surveys at Arecibo: the Local HI Universe

Ongoing Extragalactic HI Surveys at Arecibo: the Local HI Universe. Riccardo Giovanelli (Cornell University). Washington, DC, Sep07. Ongoing Extragalactic HI Surveys at AO. ALFALFA : 7000 sq.deg., 48 sec/beam, 2 mJy/bm (P.I.: R. Giovanelli, Cornell, U.S.)

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Ongoing Extragalactic HI Surveys at Arecibo: the Local HI Universe

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  1. Ongoing Extragalactic HI Surveys at Arecibo: the Local HI Universe Riccardo Giovanelli (Cornell University) Washington, DC, Sep07

  2. Ongoing Extragalactic HI Surveys at AO • ALFALFA: 7000 sq.deg., 48 sec/beam, 2 mJy/bm (P.I.: R. Giovanelli, Cornell, U.S.) • Fully blind survey, expected N>20,000 det • AGES: 300 sq.deg., 300s/beam (P.I.: J. Davies, Cardiff, UK) selected fields, expected N (scaling law)~1350 – but v likely higher • AUDS: 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)

  3. 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 a absorbers 9 OH Megamasers at intermediate redshift 10 Evolution of the HI Mass Function 11 Map local LSS in optically obscured regions

  4. 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) ? Parkes HIPASS survey: Zwaan et al. 2003

  5. 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?

  6. Leo T Slide credit: T. Oosterloo

  7. Leo T MHI = 3x105 solar MHI/LV = 5 MHI/Mbaryon = 0.8 Slide credit: T. Oosterloo

  8. Reality Check 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 Alternatively (*) Detection of an HI mass 109 solar, W=200 km/s at z=0.1 will require about 6 hrs But don’t despair: HI has been detected at AO at z=0.28 (Catinella et al. 2007)

  9. 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)

  10. HIPASS Completeness Limit HIPASS Limit

  11. 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

  12. Centroiding accuracy goes roughly as HPFW(PSF)/(S/N) 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. 1 6 2 3 ALFALFA will detect the same source with S/N~50 4 and the Arecibo beam is ¼ as wide as the Parkes one  The same source will have an ALFALFA position error of ~ 0.1’ 5

  13. AGES

  14. B. Kent Ph.D. Thesis

  15. ALFALFA: B. Kent Ph.D. Thesis

  16. B. Kent Ph.D. Thesis

  17. B. Kent Ph.D. Thesis

  18. Brown: Xray Purple: Opt Blue: HI B. Kent Ph.D. Thesis

  19. Haynes, Giovanelli & Kent 2007, ApJL

  20. v: 1915-1945 v: 1883-1915 NGC4532 v: 1852-1883 v: 1821-1852 Koopmann et al. in prep. Hoffman et al 1999 DDO137

  21. Slide credit: J. X. Prochaska 2007

  22. ALFALFA, a Legacy Survey • One of several major surveys currently ongoing at Arecibo, exploiting its multibeam capability • 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 http://egg.astro.cornell.edu/alfalfa

  23. 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

  24. 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/

  25. 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 a absorbers 9 OH Megamasers at intermediate redshift

  26. ALFALFA: Preliminary Results 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)

  27. A quick look at the Virgo Cluster

  28. B. Kent Ph.D. Thesis

  29. What about “dark galaxies”?

  30. MHI = 2x109 solar Mdyn~7x109 solar SF opt counterpart • No optical counterpart • Evidence of rotation: Vrot~13 km/s • MHI=6x108 solar • Mdyn(<3’)~7x108 solar HI 1225+01 Giovanelli & Haynes 1989 ApJ 346, L5 : Arecibo discovery Chengalur, Giovanelli & Haynes 1995 AJ 109, 2415: VLA map But do such objects exist in isolation?

  31. The Cardiff “Dark Galaxy” VirgoHI-21

  32. NGC 4254 10’ DSS2 Blue 45 kpc

  33. Minchin et al 2007 (WSRT)

  34. Combined ALFALFA data around NGC 4254cz = 2243 to 2557 km/s MHI = 5x109 solar 10’ 45 kpc Haynes, Giovanelli & Kent (2007 ApJL submitted)

  35. Combined ALFALFA data around VIRGOHI21cz = 1946 to 2259 km/s Stream MHI = 5x108 solar Minchin et al 2007 (WSRT) 10’ 45 kpc Haynes, Giovanelli & Kent (2007 ApJL)

  36. 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 work • The 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: • The 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 Myr • Hence the duration of the tidal encounter • ~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

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

  38. Duc’s simulation P-V diagram Haynes, Giovanelli & Kent 2007, ApJL

  39. 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?

  40. 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? yes no; Saintonge 2007 PhD thesis; Haynes’ talk (Basilakos et al 2007) Optically inert objects detected; see Kent et al. 2007 ApJL the latter; Haynes et al. 2007 ApJL Prob no; Saintonge 2007

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

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