A&A 386, 816-828 (2002)
DOI: 10.1051/0004-6361:20020244

The dynamical status of the cluster of galaxies 1E0657-56

R. Barrena¹, A. Biviano², M. Ramella², E. E. Falco³ and S. Seitz<sup>4

1</sup>  Instituto de Astrofísica de Canarias, 38200 La Laguna, Tenerife, Spain
²  INAF, Osservatorio Astronomico di Trieste, via G. B. Tiepolo 11, 34131 Trieste, Italy
³  Smithsonian Institution, F. L. Whipple Observatory, PO Box 97, 670 Mount Hopkins, Amado, AZ 85645, USA
⁴  Universitäts-Sternwarte, Scheinerstrasse 1, 81679 Muenchen, Germany

(Received 19 December 2001 / Accepted 12 February 2002 )

Abstract
We present the results of a new spectroscopic and photometric survey of the hot X-ray cluster , at z=0.296. We determine the presence of a low velocity dispersion subcluster, which is offset from the main cluster position by 0.7 Mpc and 600 km s ^-1. We determine the virial masses and total luminosities of the cluster and its subcluster, and solve for the two-body dynamical model. With additional constraints from the results of the analysis of the cluster X-ray emission by Markevitch et al. (2001), we find that the subcluster passed through the cluster centre 0.15 Gyr ago. Taken at face value the mass of the subcluster is typical of a loose group. It is however difficult to establish the pre-merger mass of the colliding system. We provide tentative evidence that the subcluster is in fact the remnant core of a moderately massive cluster, stripped by the collision with . The main cluster dynamics does not seem to have suffered from this collision. On the contrary, the cluster X-ray properties seem to have been significantly affected. We also discuss the effect of the subcluster collision in relation to starburst events and the cluster radio halo.

Key words: galaxies: clusters: individual: 1E0657-56 -- galaxies: clusters: general -- galaxies: distances and redshifts

Offprint request: A. Biviano, biviano@ts.astro.it

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