Issue |
A&A
Volume 467, Number 1, May III 2007
|
|
---|---|---|
Page(s) | 37 - 48 | |
Section | Cosmology (including clusters of galaxies) | |
DOI | https://doi.org/10.1051/0004-6361:20066511 | |
Published online | 05 March 2007 |
Internal dynamics of the radio halo cluster Abell 773: a multiwavelength analysis *,**
1
Instituto de Astrofisica de Canarias, C/Via Lactea s/n, 38205 La Laguna, Tenerife, Canary Islands, Spain e-mail: rbarrena@iac.es
2
Fundación Galileo Galilei – INAF, C/Alvarez de Abreu 70, 38700 Santa Cruz de La Palma, Canary Islands, Spain
3
Dipartimento di Astronomia, Università degli Studi di Trieste, via Tiepolo 11, 34131 Trieste, Italy
4
INAF – Osservatorio Astronomico di Trieste, via Tiepolo 11, 34131 Trieste, Italy
5
Centre for Astrophysics & Supercomputing, Swinburne University, Hawthorn, VIC 3122, Australia
Received:
5
October
2006
Accepted:
22
January
2007
Aims.To conduct an intensive study of the rich, X-ray luminous galaxy cluster Abell 773 at z = 0.22 containing a diffuse radio halo to determine its dynamical status.
Methods.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 Isaac Newton Telescope. We use statistical tools to
select 100 cluster members (out to ~1.8 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´ 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-1, corresponding to the velocities of the two
dominant galaxies. The low velocity structure has a high velocity
dispersion – = 800-1100 km s-1 – and its galaxies are
centred on the western 2D peak. The high velocity structure has
intermediate velocity dispersion –
500 km s-1 –
and is characterized by a complex 2D structure with a component
centred on the western 2D peak and a component centred on the eastern
2D peak, these components probably being two independent groups. We
estimate a cluster mass within 1
of 6-11
. 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 with a main cluster and having
an impact velocity ~ 2300 km s-1. In
particular, the radio halo seems to be related to the merger of the
eastern group.
Key words: galaxies: clusters: general / galaxies: clusters: individual: Abell 773 / galaxies: distances and redshifts / cosmology: observations
© ESO, 2007
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