Internal dynamics of the radio-halo cluster A2744

Abstract

We present a detailed dynamical analysis of the rich galaxy cluster A2744, containing a powerful diffuse radio halo.Our analysis is based on redshift data for 102 galaxies, part of them recovered from unexplored spectra in the ESO archive. We combine galaxy velocity and position information to select the cluster members and determine global dynamical properties of the cluster. We use a variety of statistical tests to detect possible substructures. We find that A2744 appears as a well isolated peak in the redshift space at <z>=0.306, which includes 85 galaxies recognized as cluster members. We compute the line-of-sight (LOS) velocity dispersion of galaxies (~1750 km/sec), which is significantly larger than what is expected in the case of a relaxed cluster with an observed X-ray temperature of 8 keV. We find evidence that this cluster is far from dynamical equilibrium, as shown by the non-Gaussian nature of the velocity distribution, the presence of a velocity gradient and a significant substructure. In particular, our results suggest a merging scenario of two clumps with a mass ratio of 3:1 and a LOS impact velocity (rest frame) of ~3000 km/sec, likely observed just after the core passage. The merging is occuring roughly in the NS direction with the axis close to the LOS. This scenario agrees with that proposed on the basis of recent Chandra results in its general lines, although suggesting a somewhat more advanced merging phase.

14 pages. Paper in press on Astronomy & Astrophysics

Cited by in corpus (11)

• Low-Frequency study of two clusters of galaxies: A2744 and A2219
• A2163: Merger events in the hottest Abell galaxy cluster I. Dynamical analysis from optical data
• Cluster Abell 520: a perspective based on member galaxies. A cluster forming at the crossing of three filaments?
• The dynamical status of the galaxy cluster Abell 115
• Internal dynamics of the massive cluster Abell 697: a multiwavelength analysis
• Flaming, bright galaxies along the filaments of A2744
• Internal dynamics of the radio halo cluster Abell 773: a multiwavelength analysis
• Optical analysis of the poor clusters Abell 610, Abell 725, and Abell 796, containing diffuse radio sources
• Internal dynamics of the galaxy cluster Abell 959
• XMM-Newton temperature maps for five intermediate redshift clusters of galaxies
• Global Properties of the Rich Cluster ABCG 209 at z~0.2. Spectroscopic and Photometric Catalogue