2 research outputs found
Cold fronts in cool core clusters
Cold fronts have been detected both in merging and in cool core clusters,
where little or no sign of a merging event is present. A systematic search of
sharp surface brightness discontinuities performed on a sample of 62 galaxy
clusters observed with XMM-Newton shows that cold fronts are a common feature
in galaxy clusters. Indeed most (if not all) of the nearby clusters (z < 0.04)
host a cold front. Understanding the origin and the nature of a such frequent
phenomenon is clearly important. To gain insight on the nature of cold fronts
in cool core clusters we have undertaken a systematic study of all contact
discontinuities detected in our sample, measuring surface brightness,
temperature and when possible abundance profiles across the fronts. We measure
the Mach numbers for the cold fronts finding values which range from 0.2 to
0.9; we also detect a discontinuities in the metal profile of some clusters.Comment: 6 pages, 3 figures, for proceedings of "Heating vs. Cooling in
Galaxies and Clusters of Galaxies," eds H. Boehringer, P. Schuecker, G. W.
Pratt & A. Finoguenov, in Springer-Verlag series "ESO Astrophysics Symposia.
Chemical Gradients in Galaxy Clusters and the Multiple Ways of Making a Cold Front
Cold fronts were originally interpreted as being the result of
subsonic/transonic motions of head-on merging substructures. This merger core
remnant model is theoretically justified and hold relatively well for clusters
that have clear signs of merging, such as 1E0657-56, but they do not work well
for the increasing number of cold fronts found in clusters that do not show
clear merging signs, such as A496. Here we report the results of a deeper
observation of that cluster that allowed us to produce high quality maps of the
gas parameters and to compare more closely the observations with the
predictions given by different models for cold front formation. We found for
the first time a ``cold arm'' characteristic of a flyby of a massive DM halo
near the core of the cluster. The cold arm is accompanied by an enhanced SN II
Fe mass fraction, inconsistent with the merger core remnant scenario.Comment: 3 pages, 1 figures, to appear in the Proceedings of "Heating vs.
Cooling in Galaxies and Clusters of Galaxies", August 2006, Garching
(Germany