Brendan Miller, Elena Gallo, Tommaso Treu, Jong-Hak Woo
We use the AMUSE-Virgo and AMUSE-Field surveys for nuclear X-ray emission in
early-type galaxies to conduct a controlled comparison of low-level
supermassive black hole activity within cluster and field spheroids. While both
the Virgo and the Field samples feature highly sub-Eddington X-ray luminosities
(log L_x/L_Edd between -8 and -4), we find that after accounting for the
influence of host galaxy stellar mass, the field early-type galaxies tend
toward marginally greater (0.38+/-0.14 dex) nuclear X-ray luminosities, at a
given black hole mass, than their cluster counterparts. This trend is
qualitatively consistent with the field black holes having access to a greater
reservoir of fuel, plausibly in the form of cold gas located near the nucleus.
We are able to rule out at high confidence the alternative of enhanced X-ray
activity within clusters. Presuming nuclear X-ray emission correlates with the
total energy and momentum output of these weakly accreting black holes, this
indicates that low-level AGN feedback is not generally stronger within typical
cluster galaxies than in the field. These results confirm that for most cluster
early-type galaxies (i.e., excluding brightest cluster galaxies) direct
environmental effects, such as gas stripping, are more relevant in quenching
star formation.
View original:
http://arxiv.org/abs/1112.4490
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