HI Gas as Function of Environment
When and where do galaxies stop accreting cool gas? How do they loose the cool gas? When do they stop forming stars? Oosterloo, Fraternali, Sancisi, 2007, AJ 134, 1019 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 Gas content and star formation rate begin to decline in dense group environment and outskirts of clusters
The outskirts of clusters
Solanes et al find smooth variation of HI deficiency out to 2 RA This agrees nicely with results obtained on smoothly varying star formation rate out to 2 RA In clusters at intermediate z: Balogh et al 1998 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 The outskirts of Virgo The outskirts of other (nearby) clusters The outskirts in simulations The future in HI work (clusters at z=0.2) WSRT now z: 0.164-0.224 EVLA 2011 z: 0-0.35 EVLA low freq 20?? HI Deep field….z: 0.2-1 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 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 Viva-poster Tails 2 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 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 HI stripped from NGC 4522 Kenney, van Gorkom & Vollmer 2004
NGC 4522 NGC 4522
WIYN BVR VLA HI on R
0.5L* galaxy with normal stellar disk Has only 25% of normal HI (HI def =0.6)
HI truncated in disk at 0.3R25 extraplanar HI (40% of total) on only one side of disk Disk HI grey scale, extraplanar contours; Note acceleration toward cluster mean Young Stellar Population in Stripped Outer Disk of NGC 4522
OPT + HI GALEX FUV+NUV
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 Simulations vs. HI Data in NGC 4522
Vollmer simulation Vollmer simulation HI data
50 Myr after peak pressure
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 etal 2006 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 3.5o = 0.8 Mpc from M87
• Time to reach core ~700 Myr Asca data Shibata et al 2001 M49 subcluster falling in 1300km/s ICM velocity could increase ram pressure by factor 10 ongoing stripping Just south of NGC 4522
2 tails pointing toward M49
Oosterloo and van Gorkom, 2005 HI tail probably due to ram pressure stripping Within disk HI stripped No optical counter part at position of tail Length 125 kpc .. To get that long few x 108 yr
Peaks near M86 .. High enough to get star formation In X ray.. Low temperature and high abundance region near tip of tail (Finoguenov et al 2004 XMM)
M86 group colliding with M87 and with high velocity group at 2000 km/s 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 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 A496 A2670
A85 A754 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 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
Gas loss Gas accretion
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. Ram pressure as function of distance from center
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 HI imaging of clusters at z=0.2
WSRT now
Verheijen, JvG, Szomoru, Dwarakanath,Poggianti, Schiminovich, 2007, ApJL, 688, L9 We probe a HUGE volume, 8.2Mpc x 8.2 Mpc x 18000 km/s (326 Mpc) 1.7 x 104 Mpc3 We detect galaxies…. Can even derive rotation curves
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 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 We probe a HUGE volume, 8.2Mpc x 8.2 Mpc x 18000 km/s (326 Mpc) 1.7 x 104 Mpc3 EVLA HI Deep Field
EVLA with prime focus feeds