An extension of the SHARC survey

Abstract

Aims:We report on our search for distant clusters of galaxies based on optical and X-ray follow up observations of X-ray candidates from the SHARC survey, and based on the assumption that the absence of bright optical or radio counterparts to possibly extended X-ray sources could mean that they are distant clusters.
Methods: We have obtained deep optical images and redshifts for several of these objects and analyzed archive XMM-Newton or Chandra data where applicable.
Results: In our list of candidate clusters, two are probably galaxy structures at redshifts of z∼ 0.51 and 0.28. Seven other structures are possibly galaxy clusters between z∼ 0.3 and 1. Three sources are identified with QSOs and are thus likely to be X-ray point sources, and six more also probably fall in this category. One X-ray source is spurious or variable. For 17 other sources, the data are too sparse at this time to put forward any hypothesis on their nature. We also serendipitously detected a cluster at z=0.53 and another galaxy concentration which is probably a structure with a redshift in the [ 0.15-0.6] range.
Conclusions: We discuss these results within the context of future space missions to demonstrate the necessity of a wide field of view telescope optimized for the 0.5-2 keV range.

Based on observations obtained at the Canada-France-Hawaii Telescope (CFHT), Gemini Observatory, Observatoire de Haute Provence, German-Spanish Astronomical Center Calar Alto, ESO at La Silla and Paranal, Apache Point Observatory 3.5-m telescope and on data taken from the SDSS, SIMBAD and NASA/IPAC Extragalactic (NED) Databases (see acknowledgments). Appendix A is only available in electronic form at http://www.aanda.org