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Collisional ISM Heating in Ellipticals: the Case of M86. Jeffrey Kenney (Yale) Tomer Tal (Yale) Hugh Crowl (Yale) John Feldmeier (YSU) George Jacoby (WIYN). SDSS gri. SDSS gri KPNO MOSAIC H +[NII]. NGC 4438. M86. Separation 23’ = 115 kpc. Kenney etal 2008. H velocities from - PowerPoint PPT Presentation
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Collisional ISM Heating in Ellipticals: the Case of M86
Jeffrey Kenney (Yale)Tomer Tal (Yale)Hugh Crowl (Yale)John Feldmeier (YSU)George Jacoby (WIYN)
SDSS gri
SDSS griKPNO MOSAIC H+[NII]
M86
Separation 23’ = 115 kpc
NGC 4438
Kenney etal 2008
H velocities fromWIYN Sparsepak
X-ray (ROSAT)HI (VLA)H(KPNO 4m)
NGC 4438 (Arp120)• very HI-deficient
<10% “normal” HI• ~5x109 Msun of HI
“missing”
X-Ray on H
B H
HI on B
HI: Hota etal 2007 X-ray: Machacek etal 2004
M(HI) = 2x108 Msun
M86X-ray (Chandra: Randall etal 2008) HI (VLA: Li & van Gorkom 2001)
H
Collisional KE should be significant heating source for
M86 ISM• Kinetic energy of gas stripped from
NGC 4438 by gaseous halo of M86 1/2Mv2 = 1/2 (5x109Msun)(1000 km/s)2 =
5x1058 erg
compare to:• Thermal energy of M86 ISM nkTV = (10-3 cm-3)(0.8 keV)(4/3)(73 kpc)3
= 6x1058 erg
• H evidence for a previously unknown high-velocity collision between M86 and highly disturbed spiral NGC 4438 (during subcluster merger)
• HI stripped from NGC 4438 by ram pressure during passage through M86 ISM leaves debris trail of gas heated by ram pressure drag /collisional excitation/shocks/thermal conduction (?) from hot ISM of M86, producing H filaments
Relevant for current major problem in galaxy formation/evolution: how to prevent continued star formation and stellar growth of largest galaxies
• Large collision KE~1059 erg from stripped gas should contribute to heating of M86 ISM, inhibiting “cooling flow”, star formation and BH fueling
• M86 has very weak radio source, so AGN heating of ISM unlikely at present
• Although extreme case, ISM easy to study in M86: should teach us about general importance of gravitational ISM heating in ellipticals
Kenney etal 2008
A 3rd galaxy
involved?HI tail from NGC 4388
(Oosterloo &
van Gorkom 2005)
High velocity (2000-2500 km/s) HI (WRST) and H tail from NGC 4388 (contours, green)
Low velocity (-600 to +100 km/s) H between M86 and NGC 4438 (red)
Implication for EVLA
• Some galaxies/clusters have very large range of velocities, which cannot be observed with VLA correlator
• But CAN BE with EVLA correlator
Chandra X-rayRandall etal 2008