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A textbook example of ram-pressure stripping in the Hydra A/A780 cluster

Roediger, E.; De Grandi, S.; Eckert, D.; Gaspari, M.; Gastaldello, F.; Ghizzardi, S.; Girardi, M.; Molendi, S.; Nonino, M.; Rossetti, M.

Abstract

In the current epoch, one of the main mechanisms driving the growth of galaxy clusters is the continuous accretion of group-scale halos. In this process, the ram pressure applied by the hot intracluster medium on the gas content of the infalling group is responsible for stripping the gas from its dark-matter halo, which gradually leads to the virialization of the infalling gas in the potential well of the main cluster. Using deep wide-field observations of the poor cluster Hydra A/A780 with XMM-Newton and Suzaku, we report the discovery of an infalling galaxy group 1.1 Mpc south of the cluster core. The presence of a substructure is confirmed by a dynamical study of the galaxies in this region. A wake of stripped gas is trailing behind the group over a projected scale of 760 kpc. The temperature of the gas along the wake is constant at kT ~ 1.3 keV, which is about a factor of two less than the temperature of the surrounding plasma. We observe a cold front pointing westwards compared to the peak of the group, which indicates that the group is currently not moving in the direction of the main cluster, but is moving along an almost circular orbit. The overall morphology of the group bears remarkable similarities with high-resolution numerical simulations of such structures, which greatly strengthens our understanding of the ram-pressure stripping process.

Journal Article Type Article
Publication Date Aug 1, 2016
Journal Astronomy and astrophysics
Print ISSN 0004-6361
Electronic ISSN 1432-0746
Publisher EDP Sciences
Peer Reviewed Peer Reviewed
Volume 592
Article Number A154
Pages A154
DOI https://doi.org/10.1051/0004-6361/201526641
Keywords X-rays : galaxies : clusters, Galaxies : clusters : general, Galaxies : groups : general, Galaxies : clusters : intracluster medium, Cosmology : large-scale structure
Publisher URL https://www.aanda.org/articles/aa/abs/2016/08/aa26641-15/aa26641-15.html
Additional Information This is a description of an article accepted for publication in Astronomy and astrophysics.

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