EDP Sciences
Free access
Volume 492, Number 2, December III 2008
Page(s) 345 - 354
Section Cosmology (including clusters of galaxies)
DOI http://dx.doi.org/10.1051/0004-6361:200810427
Published online 15 October 2008

A&A 492, 345-354 (2008)
DOI: 10.1051/0004-6361:200810427

The structure and dynamics of Abell 1942

H. V. Capelato1, D. Proust2, G. B. Lima Neto3, W. A. Santos3, and L. Sodré Jr.3

1  Divisão de Astrofísica, INPE/MCT, 12227-010, São José dos Campos/S.P., Brazil
2  Observatoire de Paris-Meudon, GEPI, 92195 Meudon, France
    e-mail: dominique.proust@obspm.fr
3  Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo (IAG/USP), 05508-090 São Paulo/SP, Brazil

Received 19 June 2008 / Accepted 13 September 2008

Aims. We present a dynamical analysis of the galaxy cluster Abell 1942 based on a set of 128 velocities obtained at the European Southern Observatory.
Methods. Data on individual galaxies are presented and the accuracy of the determined velocities as some properties of the cluster are discussed. We have also made use of publicly available Chandra X-ray data.
Results. We obtained an improved mean redshift value z = 0.22513 $\pm$ 0.0008 and velocity dispersion $\sigma= 908^{+147}_{-139}$ km s-1. Our analysis indicates that inside a radius of ~1.5  $h_{\rm 70}^{-1}$ Mpc (~7 arcmin) the cluster is well relaxed, without any remarkable features and the X-ray emission traces the galaxy distribution fairly well. Two possible optical substructures are seen at ~5 arcmin from the centre in the northwest and the southwest directions, but are not confirmed by the velocity field. These clumps are, however, kinematically bound to the main structure of Abell 1942. X-ray spectroscopic analysis of Chandra data resulted in a temperature kT = 5.5$\pm$ 0.5 keV and metal abundance Z = 0.33 $\pm$ 0.15 $Z_{\odot}$. The velocity dispersion corresponding to this temperature using the TX$\sigma$ scaling relation is in good agreement with the measured galaxy velocities. Our photometric redshift analysis suggests that the weak lensing signal observed to the south of the cluster and previously attributed to a “dark clump” is produced by background sources, possibly distributed as a filamentary structure.

Key words: galaxies: clusters: general -- galaxies: clusters: individual: Abell 1942 -- galaxies: kinematics and dynamics

© ESO 2008