1. HI Gas as Function of Environment

3. When and where do galaxies stop accreting cool gas? How do they loose the cool gas? When do they stop forming stars?

4. Oosterloo, Fraternali, Sancisi, 2007, AJ 134, 1019

5. 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

6. The Morphology-Density Relation It extends over 6 orders of magnitude! Postman and Geller 1984 Dressler 1980

7. Gas content and star formation rate less in dense group environment and outskirts of clusters The outskirts of clusters Solanes et al find smooth variation of HI deficiency out to 2 R A This agrees nicely with results obtained on smoothly varying star formation rate out to 2 R A In clusters at intermediate z: Balogh et al 1998 Treu et al 2003 fraction early types steep decline to 1 Mpc, gradual to 5 Mpc Regions of mean high galaxy density In 2dF : Lewis et al 2002 In Sloan: Gomez et al 2003; Nichol 2004 General conclusion star formation declines if galaxy density exceeds a certain value

8. Solanes et al 2001 Note that deficiency goes out to 2 R A

9. Possible Drivers for Environmental Evolution Gravitational galaxy galaxy : slow encounters mergers - tidal structures galaxy cluster : tidal stretching galaxy many galaxies: harassment cumulative effect of many fast encounters truncates or destroys small galaxies Affects both gas and stars Gas dynamical effects ram pressure stripping turbulent viscous stripping conduction Affects only the gas Starvation removes left over gas reservoir that fuels star formation

10. VIVA VLA Imaging of Virgo Galaxies in Atomic Gas Aeree Chung, Hugh Crowl, Kenney, van Gorkom, Vollmer Select galaxies over wide range of local densities Select galaxies with wide range of star formation properties Identify galaxies undergoing trauma Make sophisticated guess as to what is happening Use simulation to make a more sophisticated guess Compare timescales from stellar population synthesis with timescales from simulation

11. Viva-poster

12. Subgroups Small gas disks (compared to the stellar counterpart) around the cluster center Comparable or more extended than the stellar disks Small gas disk further away from the cluster center

13. Very small gas disk (blue) compared to optical In Center of Cluster

14. Tails 2

15. Can these tails be formed by ram pressure stripping? Five galaxy tails could have been formed by ram pressure N4654 probably combination of gravitational and rp N4396 possibly also, or viscous stripping

16. HI TAIL Galaxies We see for the first time galaxies being affected at intermediate distances. These are galaxies radially falling in Their gas is being removed by ram pressure and/or by gravitational interaction Chung, van Gorkom, Kenney, Vollmer, 2007, ApJ 659, L115 NGC 4522 This galaxy is different, though far out in cluster, it is stripped well to within the disk

17. HI stripped from NGC 4522 0.5L* galaxy with normal stellar disk Has only 25% of normal HI (HI def =0.6) HI truncated in disk at 0.3R 25 extraplanar HI (40% of total) on only one side of disk NGC 4522 WIYN BVR NGC 4522 VLA HI on R Kenney, van Gorkom & Vollmer 2004

18. Disk HI grey scale, extraplanar contours; Note acceleration toward cluster mean

19. Young Stellar Population in Stripped Outer Disk of NGC 4522 Strong Balmer lines and bright FUV emission in stripped outer disk indicate star formation stopped only ~100 Myr ago --> disk was stripped recently Crowl & Kenney 2006 GALEX FUV+NUV OPT + HI

20. Evidence of Ongoing Pressure from Radio Continuum in NGC 4522 Flattest spectral index (-0.7)  local electron acceleration suggestive of shock Enhanced 6cm polarization  suggests compressed magnetic field Vollmer, Beck, Kenney & van Gorkom 2004 6cm Polarized Flux on HI Spectral index 6/20 cm Eastern leading edge has:

21. Simulations vs. HI Data in NGC 4522 Large amounts of extraplanar HI close to disk truncation radius  early stage of active stripping Large extraplanar gas concentrations on both sides of minor axis --> disk-wind angle is more face-on than edge-on Vollmer simulation Vollmer simulation 50 Myr after peak pressure HI data Vollmer etal 2006

22. NGC 4522 is stripped locally and not in core NGC 4522 cannot travel far in 100 Myr, so must be stripped locally & not in cluster core NGC 4522 is located 3.5 o = 0.8 Mpc from M87 Time to reach core ~700 Myr

23. Asca data Shibata et al 2001 M49 subcluster falling in 1300km/s ICM velocity could increase ram pressure by factor 10 ongoing stripping

24. 2 tails pointing toward M49 Just south of NGC 4522

28. Oosterloo and van Gorkom, 2005

30. Crowl et al 2005

31. Conclusions from HI imaging of selected galaxies In center we see very small HI disks.. Almost certainly due to ram pressure stripping The stripping is important for the evolution of the galaxies. H alpha imaging (Koopmann Kenney 1998, 2004) shows that Virgo galaxies have reduced star formation rates compared to the field. This is primarily caused by truncation of starforming disks. A strong correlation is found between HI deficiency and normalized H alpha flux We see for the first time galaxies being affected at intermediate distances. Galaxies falling in radially are being affected by ram pressure and/or gravitational interactions Some galaxies at large distances being affected by strong rampressure. These galaxies are very HI deficient. Evidence for a dynamic ICM

32. Chung, Crowl, JvG, Schiminovich, Kenney 2008

33. Volume Limited Imaging of Clusters at 0.03< z < 0.2 Abell 1060 (Hydra), Abell 496, 85, 754, 2670 VLA Imaging 1.5x 1.5 degrees and 5000 km/s JvG, Bravo-Alfaro, Dwarakanath,Guhathakurta, Poggianti, Schiminovich, Verheijen, Wilcots, Zabludoff Abell 963 and 2192 at z=0.2 WSRT Imaging 5Mpc x 5 Mpc by 18000 km/s Verheijen, JvG, Szomoru, Dwarakanath, Poggianti,Schiminovich Boris Deshev

34. A2670 A496 A85 A754 Total HI X-ray +HI X-ray

35. Detection rates in volume limited surveys Hydra 50 galaxies pre merger A2670 50 galaxies pre merger A496 25 galaxies beginning merger A85 10 galaxies ongoing merger A 754 1 galaxy just past merger Detection rate depends on dynamical state of cluster

36. HI imaging of clusters at z=0.2 Verheijen, JvG, Szomoru, Dwarakanath,Poggianti, Schiminovich, 2007, ApJL, 688, L9

37. GALEX A963

38. We probe a HUGE volume, 8.2Mpc x 8.2 Mpc x 18000 km/s (326 Mpc) 1.7 x 10 4 Mpc 3

39. We detect galaxies…. Can even derive rotation curves

41. Stacked spectra of non detected galaxies No detection of blue B-O galaxies detection of blue field galaxies It is location of B-O galaxies that makes them different

42. EVLA versus WSRT WSRT cover from 1160-1220 MHz (18000 km/s) EVLA cover from 1420 to 1050 MHz up to z=.35 using 8192 channels of 9 km/s

43. The WSRT probes 8.2Mpc x 8.2 Mpc x 18000 km/s (326 Mpc) EVLA goes from z=0 to 0.35 in one setting

44. EVLA with prime focus feeds EVLA HI Deep Field

45. Movies by Greg Bryan (http://www.astro.columbia.edu/~gbryan/movies ) using a hybrid adaptive mesh refinement algorith gaseous component, starformation, dark matter and stars (ENZO) 1. Gas temperature: cosmological simulation of cluster assembly 2. High resolution gas density: evolution of 1 cluster 3. High resolution: HI Analysis by Stephanie Tonnesen

51. 0-1 Mpc 1-2.4 Mpc 2.4 - 5 Mpc Changes in cool gas mass for the galaxies that have no changes in stellar mass. Gas loss Gas accretion

52. Ram pressure as function of distance from center

54. Conclusions from simulations Observe mergers in central region as well as periphery, none are dry. None of the mergers exhaust gas supply of participating galaxies Ram pressure effective beyond central region, although most gas loss within 1 Mpc. Timescales 1 Gyr or more. Ram pressure begins in transition region for half of ram pressure stripped galaxies and in one case in periphery Galaxies in periphery often accrete cool gas, this stops between 1-2.4 Mpc, indicating the onset of starvation Tonnesen, Bryan, JvG, 2007, ApJ 671, 1434

55. Summary In the far outskirts of Virgo galaxies are stripped of their gas on first infall in the cluster..this affects their star formation rate and colors In a sample of nearby clusters we find that the HI detection rate depends on the dynamical state of clusters Observations and simulations suggest that as clusters assemble galaxies can be affected at large distances from cluster core.