Extended X-ray study of M49: the frontier of the Virgo Cluster
  The M49 group, resident outside the virial radius of the Virgo cluster, is
falling onto the cluster from the south. We report results from deep {\sl
XMM-Newton} mosaic observations of M49. Its hot gas temperature is 0.8\,keV at
the group center and rises to 1.5\,keV beyond the brightest group galaxy (BGG).
The group gas extends to radii of $\sim300$\,kpc to the north and south. The
observations reveal a cold front $\sim20$\,kpc north of the BGG center and an
X-ray bright stripped tail 70\,kpc long and 10\,kpc wide to the southwest of
the BGG. We argue that the atmosphere of the infalling group was slowed by its
encounter with the Virgo cluster gas, causing the BGG to move forward
subsonically relative to the group gas. We measure declining temperature and
metallicity gradients along the stripped tail. The tail gas can be traced back
to the cooler and enriched gas uplifted from the BGG center by buoyant bubbles,
implying that AGN outbursts may have intensified the stripping process. We
extrapolate to a virial radius of 740\,kpc and derive a virial mass of
$4.6\times10^{13}\,M_\odot$ for the M49 group. Its group atmosphere appears
truncated and deficient when compared with isolated galaxy groups of similar
temperatures. If M49 is on its first infall to Virgo, the infall region of a
cluster could have profound impacts on galaxies and groups that are being
accreted onto galaxy clusters. Alternatively, M49 may have already passed
through Virgo once.
