Internal dynamics of the radio halo cluster Abell 773: a multiwavelength analysis

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  • 30 January 2007
Abstract
We conduct an intensive study of the rich, X-ray luminous galaxy cluster A773 at z=0.22 containing a diffuse radio halo to determine its dynamical status. Our analysis is based on new spectroscopic data obtained at the TNG telescope for 107 galaxies, 37 spectra recovered from the CFHT archive and new photometric data obtained at the INT telescope. We use statistical tools to select 100 cluster members (out to ~1.8 Mpc from the cluster centre), to analyse the kinematics of cluster galaxies and to determine the cluster structure. Our analysis is also performed by using X-ray data stored in the Chandra archive. Results: The 2D distribution shows two significant peaks separated by ~2 arcmin in the EW direction with the main western one closely located at the position of the two dominant galaxies and the X-ray peak. The velocity distribution of cluster galaxies shows two peaks at v~65000 and ~67500 km/s, corresponding to the velocities of the two dominant galaxies. We estimate a cluster mass within 1 Mpc of 6--11 Msun. Our analysis of Chandra data shows the presence of two very close peaks in the core and the elongation of the X-ray emission in the NEE--SWW direction. Conclusions: Our results suggest we are looking at probably two groups in an advanced stage of merging. In particular, the radio halo seems to be related to the merger of the eastern group.

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