665 research outputs found
Beppo-SAX Observations of Galaxy Clusters
The high spatial resolution of the MECS experiment on board Beppo-SAX has
encouraged a few scientists, including the author, to perform observations of
galaxy clusters. Results from the analysis of the first few observed objects
are encouraging. After having reviewed the Beppo-SAX observing program for
galaxy clusters and referenced contributions to these proceedings by other
authors on the same topic, I present results from the analysis of the Perseus
cluster.Comment: 4 pages, 4 Postscript figures included. To appear in the proceedings
of the ``Active X-ray Sky: Results from BeppoSAX and Rossi-XTE'
Cold fronts in galaxy clusters
Cold fronts have been observed in a large number of galaxy clusters.
Understanding their nature and origin is of primary importance for the
investigation of the internal dynamics of clusters. To gain insight on the
nature of these features, we carry out a statistical investigation of their
occurrence in a sample of galaxy clusters observed with XMM-Newton and we
correlate their presence with different cluster properties. We have selected a
sample of 45 clusters starting from the B55 flux limited sample by Edge et al.
(1990) and performed a systematic search of cold fronts. We find that a large
fraction of clusters host at least one cold front. Cold fronts are easily
detected in all systems that are manifestly undergoing a merger event in the
plane of the sky while the presence of such features in the remaining clusters
is related to the presence of a steep entropy gradient, in agreement with
theoretical expectations. Assuming that cold fronts in cool core clusters are
triggered by minor merger events, we estimate a minimum of 1/3 merging events
per halo per Gyr.Comment: Accepted for publication in Astronomy & Astrophysics. Version with
full resolution figures available at:
http://www.iasf-milano.inaf.it/~simona/pub/coldfronts/ghizzardi.pd
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