Collisional ISM Heating in

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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)
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SDSS gri
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SDSS gri KPNO MOSAIC H?NII
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• NGC 4438

M86
Separation 23 115 kpc
Kenney etal 2008
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H? velocities from WIYN Sparsepak
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X-ray (ROSAT) HI (VLA) H??(KPNO 4m)
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H?
B
HI on B
X-Ray on H?

• NGC 4438 (Arp120)
• very HI-deficient lt10 normal HI
• 5x109 Msun of HI missing

X-ray Machacek etal 2004
HI Hota etal 2007
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M86
X-ray (Chandra Randall etal 2008) HI (VLA Li
van Gorkom 2001) H?

• M(HI) 2x108 Msun

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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

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• 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

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• Relevant for current major problem in galaxy
  formation/evolution how to prevent continued
  star formation and stellar growth of largest
  galaxies
• Large collision KE1059 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

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Kenney etal 2008
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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)

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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

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Chandra X-ray Randall etal 2008