1. Collisional ISM Heating in Ellipticals: the Case of M86
Jeffrey Kenney (Yale)
Tomer Tal (Yale)
Hugh Crowl (Yale)
John Feldmeier (YSU)
George Jacoby (WIYN)

2. SDSS gri

3. SDSS gri
KPNO MOSAIC H+[NII]

4. NGC 4438
M86
Separation 23’ = 115 kpc
Kenney etal 2008

5. H velocities from
WIYN Sparsepak

6. X-ray (ROSAT)
HI (VLA)
H(KPNO 4m)

7. very HI-deficient <10% “normal” HI ~5x109 Msun of HI “missing”B H
HI on B
X-Ray on H
NGC 4438 (Arp120)
very HI-deficient <10% “normal” HI
~5x109 Msun of HI “missing”
HI: Hota etal 2007
X-ray: Machacek etal 2004

8. M86 X-ray (Chandra: Randall etal 2008) HI (VLA: Li & van Gorkom 2001)
M(HI) = 2x108 Msun

9. 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

10. 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

11. 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

12. Kenney etal 2008

13. A 3rd galaxy involved? HI tail from NGC 4388 (Oosterloo & van Gorkom 2005)
High velocity ( 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)

14. 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

15. Chandra X-ray
Randall etal 2008