27-10-2012, 02:08 PM
OVER LUMINOUS ELLIPTICAL GALAXIES
ABSTRACT
The first paper from our work has been completed and accepted for publication. Another paper presents a study of the
ESO 30601 70 galaxy group, combining Chandra, XMM-Newton, and optical observations. We find that the system is a true
fossil galaxy group - a group whose optical light is dominated by a single galaxy. The group X-ray emission is composed of
a central, dense, cool core (10 kpc in radius) and an isothermal medium beyond the central 10 kpc. The region between 10
and 50 kpc (the cooling radius) has the same temperature as the gas from 50 to 400 kpc, although the gas cooling time between
10 and 50 kpc (2-6 Gyr) is shorter than the Hubble time. Thus, the ESO 3060170 group does not have a group-sized cooling
core. We suggest that the group cooling core may have been heated by a central active galactic nucleus (AGN) outburst in
the past and that the small, dense, cool core is the truncated relic of a previous cooling core. The Chandra observations also
reveal a variety of X-ray features in the central region, including a finger, an edge-like feature, and a small tail, all aligned
along a north-south axis, as are the galaxy light and group galaxy distribution. The proposed AGN outburst may cause gas
to slosh around the center and produce these asymmetric features. The observed flat temperature profile to 1/3rvir is not
consistent with the predicted temperature profile in recent numerical simulations. We compare the entropy profile of the ESO
3060170 group with those of three other groups and find a flatter relation than that predicted by simulations involving only
shock heating, S approximately r approximately 0.85. This is direct evidence of the importance of non-gravitational processes
in group centers. We derive the mass profiles within 1/3rvir and find that the ESO 3060170 group is the most massive fossil
group known.