1. Eric M. Wilcots University of Wisconsin-Madison

2.  How and when did galaxies accrete their gas?  Where and when did/do galaxies stop accreting gas?  How do galaxies lose their cool gas?  How does star formation get started?

3.  Now have HI detections to z~0.2 (Verheijen, van Gorkom et al, Catinelli et al.)  This is fantastic, but there is lots of galaxy evolution beyond this…

4. Star formation directly seen in the rest-frame UV GALEX, Wyder et al. 2005 GALEX, Schiminovich et al. 2005 Wilson et al. 2002 Bouwens et al. 2005 Bunker et al. 2005 Steidel et al. 1999 Iwata et al. 2003 Bouwens et al. 2002 Wang, Cowie, & Barger 2006

5. Comparison of the FIR-determined star formation with the UV-determined star formation Directly measured FIR star formation Maximal corrections for missing EBL, if at z=1-3 Star formation rate density for a Salpeter IMF extending to 0.1 M(sun) x the cosmic time

6.  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?

7. Evolution of the FIR luminosity of the radio source population – downsizing? Barger, Cowie, Wang 2007

8. Strength of red sequence in clusters decreases from z~0.4 to z~0.9 Cluster luminosity function evolves (Gilbank et al 2008)

9. Galaxy luminosity functions from Red Sequence Cluster Survey (Gilbank et al 2008)

10.  Neutral gas density in Universe (from Lah et al. 2007). z=0 triangle is from HIPASS, large triangle is new GMRT measurement. High redshift points come from damped Ly-  measurements. Note large uncertainty in redshift range z = 0.1 – 1.5, corresponding to 2/3 age of Universe.

11. Rao et al. 2006 ApJ 636 610 Evolution in density of damped Ly-alpha systems

12.  …the evolution of the HI content of galaxies to z~2… ◦ Deep (~10ks) EVLA surveys of the HI content of galaxies to z~0.5; push beyond z~0.5 (GMRT, ASKAP, MeerKAT)

13.  Current generation ALFA surveys will yield ~several x 10 4 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)

14.  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 deg 2 – depends on success of PAF technology - N=600,000 Z=0.05 Johnston et al. 2007

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

16. …the evolution of the HI content of galaxies to z~1… – Deep (3-10Ks) EVLA surveys of the HI content of galaxies to z~0.5; push beyond z~0.5 (GMRT, ASKAP, MeerKAT)

17. satellite accretion – 10 8 M worth of gas in Local Group for MWG accretion – Accretion of gas-rich companions rare in the nearby Universe – (e.g. Pisano & Wilcots 2003)

19. satellite accretion – 10 8 M worth of gas in Local Group for MWG accretion – Accretion of gas-rich companions rare (e.g. Pisano & Wilcots 2003) Condensation of thermal instabilities in hot halos – galactic “rain”? – NGC 891, head-tail clouds, etc – But….

20. Lowest contour ~ 5 x10 18 cm -2

21. NGC 5746 – Rand & Benjamin 2008

22. Halo Gas Extended HI around galaxies – Minchin et al (2003) – 4.2 x 10 18 cm -2 in Centaurus – Westmeier, Braun, Thilker (2005) – 9 x 10 17 cm -2 around M31 Ionization edges of galaxies – what is the true extent of the HI disk? – N(HI) = 1.6 x 10 17 cm -2 –optical depth at the Lyman edge ~ 1 (Corbelli, Salpeter, & Bandiera 2001) Goal: connect HI in emission around galaxies to Lyman Limit Systems

23.  …the evolution of the HI content of galaxies from z~1 to z=0….  …the complete census of HI clouds/emission in the halos of nearby galaxies arising from the condensation of hot gas… ◦ This requires surface brightness sensitivity (i.e. high filling factor arrays) plus resolution

24.  Radio continuum sources more numerous in the outskirts of Red Sequence Clusters (Gladders)  Galaxy groups more active in the outskirts of clusters (Carlberg et al. 2002)  Galaxy transformation vs environment  HI mass function varies with environment  Optical luminosity function varies with environment

26. The lore.. if halos get too big, gas does not cool But.. at least some dry mergers are wet, and forming stars Donovan, Hibbard, an Gorkom, 2007, AJ 134, 1118

27. Mulchaey & Zabludoff ~30% of the total HI is in the tidal material

28.  Interaction rate much higher in spiral-dominated groups.  Spiral dominated/HI rich  elliptical dominated/X-ray rich  “Unattached” HI clouds (merger remnants) more common in elliptical dominated groups  Conversion of neutral gas into hot gas takes place with the intragroup medium and not in individual galaxies

29. HI detections All members X-ray emission

30. …the evolution of the HI content of galaxies from z~2 to z=0…. …the complete census of HI clouds/emission in the halos of nearby galaxies arising from the condensation of hot gas… …the environmental impact statement… – e.g. A THINGS in and around clusters – Infall regions is where the action is – the Red Cluster Sequence survey will have 500 clusters; we have complementary HI data for <20.

31.  This is mostly ALMA science since stars form out of molecular gas….  but a little high resolution HI data might help…

33. …the evolution of the HI content of galaxies from z~2 to z=0…. …the accretion of gas onto galaxies… …the complete census of HI clouds/emission in the halos of galaxies arising from the condensation of hot gas… …the environmental impact statement… …fine scale structure of the ISM in star- forming galaxies…