M. Pierre et al., OPTICAL OBSERVATIONS OF A ROSAT SAMPLE OF CLUSTERS OF GALAXIES .1. TECHNIQUES AND X-RAY OPTICAL ANALYSIS, Astronomy and astrophysics, 290(3), 1994, pp. 725-752
The applications of clusters of galaxies to cosmology are multiple and
currently of special importance; it is thus of great interest to cons
truct large unbiased samples. We present here the first results from o
ptical follow-up observations of a ROSAT subsample of 42 clusters of g
alaxies in a contiguous area covering about 1700 square degrees. The g
eneral detection and selection procedures from the ROSAT All-Sky Surve
y adopted for clusters are described in detail. Further optical identi
fications of the cluster candidates and the measurement of their redsh
ifts at the 3.6m ESO Telescope are presented. Various optical/X-ray co
rrelations are investigated. Special care is given to the study of the
significance of the observed cluster X-ray morphologies. X-ray contou
r plots for all clusters are shown, and for 31 objects, overlays on to
p of CCD images are presented in order to outline the correlation betw
een optical and X-ray morphologies in detail and to flag possible cont
amination by unrelated point-like objects.