Cold fronts and multi-temperature structures in the core of Abell 2052
  The physics of the coolest phases in the hot Intra-Cluster Medium (ICM) of
clusters of galaxies is yet to be fully unveiled. X-ray cavities blown by the
central Active Galactic Nucleus (AGN) contain enough energy to heat the
surrounding gas and stop cooling, but locally blobs or filaments of gas appear
to be able to cool to low temperatures of 10^4 K. In X-rays, however, gas with
temperatures lower than 0.5 keV is not observed. Using a deep XMM-Newton
observation of the cluster of galaxies Abell 2052, we derive 2D maps of the
temperature, entropy, and iron abundance in the core region. About 130 kpc
South-West of the central galaxy, we discover a discontinuity in the surface
brightness of the hot gas which is consistent with a cold front. Interestingly,
the iron abundance jumps from ~0.75 to ~0.5 across the front. In a smaller
region to the North-West of the central galaxy we find a relatively high
contribution of cool 0.5 keV gas, but no X-ray emitting gas is detected below
that temperature. However, the region appears to be associated with much cooler
H-alpha filaments in the optical waveband. The elliptical shape of the cold
front in the SW of the cluster suggests that the front is caused by sloshing of
the hot gas in the clusters gravitational potential. This effect is probably an
important mechanism to transport metals from the core region to the outer parts
of the cluster. The smooth temperature profile across the sharp jump in the
metalicity indicates the presence of heat conduction and the lack of mixing
across the discontinuity. The cool blob of gas NW of the central galaxy was
probably pushed away from the core and squeezed by the adjacent bubble, where
it can cool efficiently and relatively undisturbed by the AGN. Shock induced
mixing between the two phases may cause the 0.5 keV gas to cool non-radiatively
and explain our non-detection of gas below 0.5 keV.
