M. Pierre, N. Clerc, B. Maughan, F. Pacaud, C. Papovich, C. N. A. Willmer
Context: Very few z > 1.5 clusters of galaxies are known. It is important to
study the properties of galaxies in these clusters and the ICM and, further, to
cross-check the reliability of the various mass estimates. This will help to
clarify the process of structure formation and how distant clusters may be used
to constrain cosmology. AIMS: We present a 84 ks Chandra observation of
IRC-0218A, a cluster of galaxies inferred by the presence of a galaxy
overdensity in the infrared at a redshift of 1.62 and associated with some XMM
emission Methods: Spatial analysis of the Chandra X-ray photon distribution.
Results: The Chandra observation of IRC-0218A appears to be entirely dominated
by a point-source located at the centroid of the MIR galaxy density. In
addition, we detect weak extended emission (2.3 sigma) out to a radius of 25"
with a flux of ~ 3 10E-15 erg/s/cm2 in the [0.3-2]keV band. Assuming that
clusters evolve similarly, we infer a virial mass of M200 =7.7+/-3.8 10E13Mo.
This is marginally compatible with our current estimate of the cluster
dynamical mass (based on 10 redshifts), although there is no evidence that the
galaxy peculiar velocities correspond to the motions of a virialized structure.
The stellar mass enclosed in the inferred X-ray virial radius is estimated to
1-2 10E12 Mo. We provide a detailed account of 28 X-ray point-sources detected
in the field.
View original:
http://arxiv.org/abs/1109.6194
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