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Session 95 - X-Ray Galaxies and Clusters.
Oral session, Wednesday, January 17
La Condesa, Hilton
The availability of numerous deep PSPC and HRI pointings in the ROSAT pointing archive presents an ideal opportunity to extend our knowledge of moderate and high redshift X-ray clusters. We are in the process of constructing a large sample of serendipitously detected z>0.3 X-ray clusters from all b>30^\circ, t>10ksec pointings accessible to the 3.5 metre ARC telescope. Using deep imaging in two colours we will search for evidence of faint galaxy clustering around all extended sources that have no counterpart on the Palomar sky survey or in the NED database. The wavelet transform technique is used to both locate sources and to define their extents. To date, 1784 sources have been detected in 94 PSPC pointings, allowing us to define very accurately the PSF as a function of off-axis angle. On average one cluster candidate is selected for optical follow-up from each pointing. Analysis of the 45 images obtained so far demonstrates that at least one third of the X-ray sources in our candidate list are surrounded by a dense knot of galaxies that are too faint to be visible on the Palomar survey plates. Spectroscopic follow-up is planned to confirm the presence of a cluster and derive the cluster redshift in these cases. In addition to the X-ray processing and optical follow-up, extensive modelling is taking place to define the selection function of our cluster sample. We present a progress report on these three aspects of the SHARC survey as well as a discussion of the motivation and goals of the project.
