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The HI Universe: The ALFA and the Omega(HI)

The HI Universe: The ALFA and the Omega(HI). Patricia Henning Cosmic Web: galaxies and the large-scale structure Socorro NM, 16 May 2008. HI surveys – the past. HI Parkes All Sky Survey - HIPASS (2004; Meyer, Zwaan et al.) All southern hemisphere, plus northern extension to Dec = +25 deg

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The HI Universe: The ALFA and the Omega(HI)

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  1. The HI Universe: The ALFA and the Omega(HI) Patricia Henning Cosmic Web: galaxies and the large-scale structure Socorro NM, 16 May 2008

  2. HI surveys – the past • HI Parkes All Sky Survey - HIPASS (2004; Meyer, Zwaan et al.) • All southern hemisphere, plus northern extension to Dec = +25 deg • 5300 galaxies over 70% of sky • sensitivity 13 mJy per 15 arcmin beam, at 18 km/s velocity resolution • 64 MHz BW, -1280 – 12,700 km/s • 280 galaxies with log MHI < 8.5 in south

  3. Meyer et al. 2004

  4. A deeper southern hemisphere Galactic plane survey

  5. New New Part of Norma SC PKS1343 cluster New Puppis void Puppis Hydra wall and Monoceros extension

  6. Extragalactic Arecibo L-band Feed Array (ALFA) Surveys • Arecibo Legacy Fast ALFA (ALFALFA) Team leaders: Giovanelli, Haynes (Cornell) • Arecibo Galaxy Environments Survey (AGES) Team leader: Davies (Cardiff) • ALFA Ultra-Deep Survey (AUDS) Team leader: Freudling (ESO) • Zone of Avoidance Survey (ALFA ZOA) Team leader: Henning (UNM)

  7. ALFA surveys • Arecibo Legacy Fast ALFA Survey - ALFALFA • Ongoing, planned 7000 deg2 of high-galactic latitude Arecibo sky • ~2.2 mJy per 3.5 arcmin beam, at 10 km/s velocity resolution • 100 MHz BW, -1600 – 18,000 km/s (+ new broad-band spectrometer?) • 30,000 expected detections in ~5 years, to z=0.06, hundreds of objects to HI mass to 108

  8. Wedge plot of 2700 HI sources detected with ALFALFA (with 7.5% of survey) Z=0.05

  9. ALFA Surveys (cont) • Arecibo Galaxies Environment Survey - AGES • Ongoing, planned 200 deg2 total on 13 selected areas (Virgo, groups, individual gals, filaments, Local Void) • ~0.8 mJy per 3.5 arcmin beam (300 vs. 40 sec per beam), at 10 km/s velocity resolution • Will find low-mass galaxies to larger distances, but not as large-angle survey

  10. Sky dist. and HI mass vs. distance for 100 HI sources in AGES Abell 1367 region sample (Cortese et al.). Solid line detection limit S/N=6.5, W=200 km/s, dotted line same for ALFALFA, dashed HIPASS

  11. ALFA Surveys (cont) • Arecibo Ultra-Deep Survey – AUDS • Strategy: very long integration time on small patches of sky • ~1000 hours on 0.36 square degree field, 75 hours/beam, few x108 M0 at z=0.16 • Stats should be sufficient to discriminate strong evolution vs. no-evolution scenario • Done precursor obs, not full sensitivity survey yet

  12. More science goal for AUDS • The cosmic web (reach ~1016 cm-2 per 5 km/s channel, gas filling beam) • Low column density gas in the local Universe • Extragalactic OH megamaser emission • Extragalactic HI absorption

  13. The ALFA ZOA survey • Map obscured galaxies, large-scale structures at low Galactic latitude • Provide redshifts for partially-obscured galaxies, particularly 2MASS for all-sky flow fields • Two phases: shallow (5 mJy), deep (1 mJy) • Deep survey will have ~sensitivity of AGES over ~2-4 times sky area, HIMF study over “fairer” volume

  14. Local void Orion void? Delphinus void Gemini void Puppis filament Microscopium void A569 Cygnus void Canis Major void Pisces-perseus supercluster A539

  15. Define edges of the Gemini, Canis Major, Microscopium, and Cygnus voids • Determine reality of Orion void • Confirm/Refute connection between A539 and A569 • Probe newly-discovered nearby Monoceros filament • Study HI in variety of densities, survey region not selected by LSS

  16. ALFA ZOA survey status • Survey began May 2008 - Hundreds of hours, starting in inner Galaxy, ~1000 square degrees • Have completed two small, shallow “precursor” regions (38 sq deg near l=40, 100 sq deg near l=190)

  17. Inner Galaxy: 10 galaxies detected, only 1 has a cataloged counterpart in any other waveband (IR)

  18. Outer Galaxy: 62 galaxies detected, 49 have counterparts 25 previous redshifts

  19. Beyond ALFA • Current generation ALFA surveys will yield ~several x 104 galaxies to z~0.1, will characterize the local HI mass function very well. (Arecibo capable of going deeper, but confusion issues for high z, especially for blind surveys – beam about size of a cluster at z=0.25) • HI detection beyond z = 0.1 has been achieved eg. z=0.28 with AO (Catinella et al.) also z=0.2 WSRT (Verheijen et al.) and z=0.24 in aggregate sense with GMRT (Lah et al.)

  20. Neutral gas density in Universe (from Lah et al. 2007). z=0 triangle is from HIPASS, large triangle is GMRT measurement. High redshift points come from damped Ly-a measurements. Consistent with constant! (note uncertainty in redshift range z = 0.1 – 1.5, corresponding to 2/3 age of Universe)

  21. Cosmic star formation history (Panter et al. 2007) • Want record of HI over redshift with large evolution in SFR – where, how, is gas going to stars?

  22. The next step • A Goal: Evolution of HIMF. Most of the action should be between z=0-1, MHI=(0.4 – 4) x 109 Msun (vd Hulst et al. 2004) Predicted evolution of HIMF in hierarchical picture (Baugh et al. 2004). Dots are measured z=0 (Zwaan 03). Lines are predictions: solid z=0, dotted z=1, dashed z=3, dot-dashed z=4

  23. Square Kilometer Array pathfinders • E.g. ASKAP, 700-1800 MHz, with strawman 30 12m dishes with PAF, upgrade/expansion to 45. 5-sigma detections for all southern-hemisphere, “shallow” (1 yr) survey strawman, expansion FOV 30 deg2 – depends on success of PAF technology - N=600,000 Z=0.05 Johnston et al. 2007

  24. ASKAP (cont.) Z=0.2 Johnston et al. 2007 Similar simulation for a deep (1 yr) single pointing, N= 100,000

  25. New pathfinders include • ATA – currently ATA-42, 6m dishes, FoV 2.45 deg at 21cm. Full array could do deep HI • MeerKAT – design decisions ongoing, aim 80 12m dishes, single pixel feeds • APERTIF/WSRT – developing FPA on WSRT, 25x FOV, 2x BW of current WSRT • FAST – 500m dish, significant funding, design developing

  26. What’s next? • Next science step must be significant, or not worth funding • Big step forward could be HIMF to z=1 • Want SB sensitivity, but also want resolution to assign proper HI mass (e.g. at z=1, 20”=160 kpc, 5 km baseline)

  27. 10% SKA • At z=1, reach 3.6 x 109 Msun in 360 hours, 2.1 x 109 Msun in 1000 hours (Draft Phase I science case) But descope??? • To reach 5 x 108 Msun ~750 day survey with 10% SKA. Long time, but worthwhile • If few pointings, long time, then prefer large FoV (of course)

  28. Key Science Project for the full SKA – 109 HI galaxies to z=1.5, for galaxy evolution, Cosmology (BAO)

  29. Timescales, Questions • ALFA surveys complete ~5 years, new pathfinders underway • Connection to multi-l: large optical/IR surveys (e.g. LSST) going concerns in the 2010’s, time will be ripe for deep HI surveys • When/how do we best join forces with international community given US funding realities? Timescales plausible? SKA must be capable instrument…Descope troubling… • Coordinate with other SKA-mid science/tech issues: mid-freq Radio Synoptic SKA

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