[Normal Galaxies, Clusters of Galaxies -- Oral ]
NGC7618 and UGC12491: Gas-Dynamics in the Nearby Merger of Two
Sub-groups
Marie Machacek, SAO
R.P. Kraft (SAO), C. Jones (SAO), W.R. Forman (SAO), P.E.J. Nulsen (SAO), S.S. Murray (SAO), M.J. Hardcastle (Univ. of Hertfordshire)
Most galaxy evolution is found to occur in moderately massive
galaxy groups, that, in hierarchical models of structure formation, may
themselves be merging along filaments to form more massive structures.
The study of nearby examples of galaxy and subgroup mergers, where
Chandra's high angular resolution allows us to directly observe X-ray
edges, outflows, and tails detailing the dynamical processes at work, is
key to understanding the properties of galaxies, their central supermassive
black holes, and the surrounding intracluster medium observed today. We
present results from two ~30 ks Chandra observations of NGC7618 and
UGC12491, respectively, and a 25 ks XMM-Newton MOS+pn observation of the
NGC7618/UGC12491 system, together tracing gasdynamical interactions in
one of the best examples of an ongoing subgroup-subgroup merger in the
local universe. We find X-ray surface brightness discontinuities and
temperature asymmetries around the two dominant subgroup galaxies,
NGC7618 and UGC12491, but with strikingly different morphologies. We
discuss the likely origin of these gas morphologies. We use imaging and
spectral analyses of the observed surface brightness and temperature
features to measure the density, pressure and entropy in and surrounding
NGC7618 and UGC12491 to constrain the kinematics of the merger and test
models for gas stripping, 'sloshing' and entropy evolution in the
sub-group gas, and possible feedback from AGN activity that may have
been triggered by the merger.