Aspen Summer Session 5/28/03 Mazzotta Cold Fronts in clusters ========================= seen in merging clusters A2142 Markevitch et al. 00 discontinuity in Surface Brightness Profile T inside lower wrt outside -> not shock where it would be opposite ->density discontinuity (lower outside of front) Also seen in A3667 Vikhlinin et al. 00 best studied interpretation: moving dense,cold gas clud moving wrt hot lower density ambient gas pressure ratios far from front vs. inside front gives cloud spleed external gas slows at leading edge of cloud; accelerates going around sides simulations: Nagai & Kravtsov 02 ApJL support above interpretation Bialek et al. 02 show DM more extended than gas What about apparently relaxed clusters? Yes, sometimes seen RXJ1720.1+2638 appears round also Mazzotta et al. 01b submitted MS1455.0+2232 Markevitch et al. 01 ApJ A1795 How many cold fronts can be observed? Depends on direction of cloud motion wrt plane of sky Even if motion is only 30 deg wrt sky plane, can't see it! At most you can only see 1/3 of existing fronts Markevitch et al. in prep claim see cold fronts in 2/3 of Edge et al. sample -> Therefore all clusters have AT LEAST 1 front! Chandra images of 2A0335 show fronts but lots of clumps, substructure X-ray blobs don't coincide with optical galaxies There is diffuse Halpha emmission disrupted by xray blobs Also radio halo which fills xray holes Temp map shows complexity; blobs have variety of apparent Ts If deproject; get ~same T as rest of cluster -->but then must have higher pressure reasons for fronts in round clusters ->high impact param merger - NO; too many seen ->remnant of recent merger w/ sloshing ->radio halo effect radio bubble makes sound wave that generates sloshing at large radius is there AGN with multiple outbursts, each one producing a pair of bubbles that buoy up This has strong implications for kinematic SZ effect and CMB polarization by clusters ->high gas velocity in moving clusters; higher than cluster peculiar velocities; since bubbles are dense; can provide factor of 3 increase in SZ effect. Polarization goes as vel.^2 so can be order of mag increase Q&A Voit: can fronts be used to weigh mergers or get merger history? A: combining front+SZ(v_radial)+pol(v_tan) cab get info on incoming direction of merger but not all fronts due to ongoing mergers. Can be remnants or AGN; therefore may not be so good... Ricker: can we distinguish merger vs. bubble fronts? A: No, but since seen so many in "round" clusters, unlikely to be mergers ===================================================================================== ===================================================================================== Oliver Czoske High Speed COllision Cl0024+1654 Strong lensing cluster at z=0.395 5 images of spiral at z=1.675 vel disp=1200km/s from dressler 99 with ~100 zs Tyson et al. 1998 mass reconstruction -flat core ; isi t due to misplaced center? X-ray: Lx=6.7*10^43 ; factor of 2-3 mass discrep betw. methods optical spectr: 650 redshifts in wide area survey; 300 in cluster has foreground component; not expected from previous data outskirts show redshift outer clumps NOT SEEN from just 100 z's long tight bridge between main cluster & foreground clump -> high speed collision where smaller cluster smashed through main cluster; core decelerated -> if mass ratio high; core of smaller guy destroyed -> if mass ratio 2:1; cores remain but superposed --> this leads to projected mass profile that matched that from lensing --->not problem for CDM Q&A Voit: How often do you get such collisions A: (Evrard) Good question. But see typical mergers result in NFW once in equilibrium; maybe this is unusual example. (Speaker) See 3000km/s mergers reasonably often (Evrard) Once relaxed this will go to NFw oLD GUY: constraints on direction wrt LOS A: should be very close to LOS since cores not separable Q: Are individual cores NFW and just appear flat in proj? A: No, both cores are heated. Consequences: Vel. disp bad for M_est gas not in hydro eq. -> Lx, Tx not good mass measure Lensing gives projected mass so not good either! HST imaging with WFPC2 39 pointings scattered over area -weak lensing shows mass elongation/secondary peak associated with another infalling group also seen in spectroscopy -main cluster gives insane concentration but with conceivable mass -including strong lensing improves constraints but with same results -so NFW profile used in models not good -go to simulations; get parametrized profile to compare with NFW ========================================================================================== ========================================================================================== Paul Ricker Not-So-Tiny Bubbles Relaxed clusters show interaction of active AGN with ICM bubbles of magnetized plasma that displace and heat gas mixing efficiency? cooling flow shutfoof? fraction of cluster energy budget? sims say they are late stages of AGN jets with continuous energy injection can shut off cooling FLASH code parallel AMR hydro code to examine bubbles in stratified atmos -hydro only bubbles quickly disrupted by fluid instabilities, regardless of bubble density -pressure supported bubbles with external B fields -strong field can prevent disruption; but needs to be very high -magnetically supported bubbles -maintains shape ; may have ring of bright material and wake Voit: Popular AGN heating mechs suggest cooling time increased due to gas mixing, or turbuelence creation & dissipation. Not seen in Ricker's magnetic bubbles. Kravtsov: But Ricker's model has unrealistic cluster ; no structure etc. Edge: What happens when bubble hits cold front? Can you liberate energy? Old guy: transience of bubbles? Ricker: simulation has optimal condition so 200million years is prbably far upper limit. Old guy: What does this say about AGN jet duty cycle? Ricker: not much; different scales. Duty cycle would be input to calculation Mazzarrota: radio quiet bubbles seen with longer lifetimes A: maybe different mechanism ========================================================================================== ========================================================================================== Caleb Scharf Xray observations of clusters Cl1226 11.5kev z=0.89 not unexepected in WMAP cosmology (expect 0.3) cl0152 z=0.83 xmm image shows amazing structure; 2 cores, cold regions M~10^15 Msun Should finish merging in 4Gyr or so how to count such clusters? Took brightest submm source, also radio galacy 4c4117 take Chandra image;is it protocluster region? object detected; point source w/extended fuzz and some nearby point sources w/ same z 150kpc extension with power law spectrum; same index as radio emission so may be inverse compton; much higher SB than typical cluster thermal emission very bright FIR source +CMB can produce this Ly-alpha image at Keck shows impressive messy object with cusps, blobs etc. some correlation of lya radio xray early version of bubbles? Voit: mother of all feedback events? Is it common? Can every large cluster have one? A: common if most radio sources at hi-z are associated with this. Submm surveys too small. Chandra prop to look at submm+radio sources to see if they have inv. compton x-ray Maybe inv. compton helps sustain Lya halo Q: What about other nearby sources? A: at least one also Lya and submm emitter. Field overdense in xray pt sources, lya emitters, etc. ========================================================================================== ========================================================================================== Massimo Meneghetti Arc statistics with cluster simulations arc #s (all sky) determined by cluster abundance at hi-z,lens conc & dens prof & substructure -all driven by cosmology Analytic models not good due to asymmetry, substructure, etc.; can make factor of 100 difference in lensing cross-section. Use ray-trace models on nbody sims early numerical models Bartlemann 98 - expect giant arcs 10 SCDM 100 LambdaCDM 1000 OpenCDM Observed: Gladders 03, Zaritsky 03, Luppino 99 0.2-0.3 giants arc/massive cluster -->3000 giant arcs all sky suggest OCDM based on Bartelmann. But if substructure......can we understand why LCDM is not best match, even though all other experiments support LCDM ---Bartlemman had low res; no individual galaxy halos -compare low, hi res sims -hi res: split large arcs (seen in data), small arcs can be magnified -cancel out; arc statistics not changed much --consider addition of massive cD; change density profile. lensing cross sec increases by 50% not sufficient to get order of mag.... Kravtsov: Did you account for steepening of DM profile? A: NO what about merger effects? Need high time resolution; timescal of events 1Gyr Simulated cluster merger; study delta lensing cross sec during 1Gyr merger during merger, elongation of critical lines grows, then overall expansion, shrinking Cross sec increases by x10, then drops to lower value If clusters selected by Xray may preferentially select such clusters Why not see in Bartlemann? Need lots of clusters (only 9 in Bartelmann) to see these rare events Yee: compare clusters with 2 vs. 1 giant arc Zabludoff: If clusters cross many times before merger may have multiple events that increase cross section ========================================================================================== ========================================================================================== Tormen ICM Dynamics survival of lumps in mergers, thermalization time observable signatures? how long can they be seen? density, flux,temp maps from sims compute self-bound mass frac for gas & dm as f(t,m/M) for small mergers, DM & gas separate (no dyn fric on DM); gas falls in center quickly major mergers - potential of merging object strong enough to hold most of gas -come to rest in 3-4gyr satellite velocity dispersion increases, much more for small merger gas. gas heated in 2gyr for all cases but DM heated slower 4gyr For particles that are bound to infalling object -major merger - cooling! of infalling things. Zabludoff: This suggests vel disp more consistent mass estimate than T.