Intragroup and Galaxy-Linked Diffuse X-ray Emission in Hickson Compact Groups. (arXiv:1212.1151v1 [astro-ph.CO])

Intragroup and Galaxy-Linked Diffuse X-ray Emission in Hickson Compact Groups. (arXiv:1212.1151v1 [astro-ph.CO]):
Isolated compact groups of galaxies (CGs) present a range of dynamical
states, group velocity dispersions, and galaxy morphologies with which to study
galaxy evolution, particularly the properties of gas both within the galaxies
and in the intragroup medium. As part of a large, multiwavelength examination
of CGs, we present an archival study of diffuse X-ray emission in a subset of
nine Hickson compact groups observed with the Chandra X-ray Observatory. We
find that seven of the groups in our sample exhibit detectable diffuse
emission. However, unlike large-scale emission in galaxy clusters, the diffuse
features in the majority of the detected groups are linked to the individual
galaxies, in the form of both plumes and halos likely as a result of star
formation or AGN activity, as well as in emission from tidal features. Unlike
previous studies from earlier X-ray missions, HCGs 31, 42, 59, and 92 are found
to be consistent with the Lx-T relationship from clusters within the errors,
while HCGs 16 and 31 are consistent with the cluster Lx-sigma relation, though
this is likely coincidental given that the hot gas in these two systems is
largely due to star formation. We find that Lx increases with decreasing group
HI to dynamical-mass ratio with tentative evidence for a dependance in X-ray
luminosity on HI morphology whereby systems with intragroup HI indicative of
strong interactions are considerably more X-ray luminous than passively
evolving groups. We also find a gap in the Lx of groups as a function of the
total group specific star formation rate. Our findings suggest that the hot gas
in these groups is not in hydrostatic equilibrium and these systems are not
low-mass analogs of rich groups or clusters, with the possible exception of HCG
62.