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M. E. Donahue, C. Scharf, J. Mack, P. Lee, M. Postman, M. Dickinson (STScI), P. Rosati (ESO), J. Stocke (UColo)
We present a summary of results of the Rosat Optical X-ray survey, a survey utilizing both X-ray and optical detection techniques to reveal the locations and to estimate the properties (redshift, optical and X-ray luminosities) of clusters of galaxies. The matched filter algorithm of Postman and Lauer is used to detect galaxy clusters in galaxy catalogs (limiting magnitudes of I~23) of CCD images of the central 30' by 30' of extragalactic Rosat fields with relatively long exposure times. We identify X-ray cluster candidates with a wavelet technique developed by Rosati. We identify 57 cluster candidates, of which 35 targets were unaffected by bright stars, confusion, or uncertain X-ray fluxes; we identify 147 optical candidates in the same fields with a formal significance of >3. Thirty one out of 35 X-ray clusters were detected optically; 26 of these are very secure cross-IDs. A more subjective inspection of the optical candidates revealed that at least 57 of these clusters appear optically significant yet have no X-ray counterpart. We present an analysis of these results and we conclude that the estimated optical luminosities of candidates have more scatter relative to the clusters' masses than do the X-ray luminosities. A prediction can be made that X-ray faint clusters are low-mass clusters with correspondingly low temperatures and weak lensing signatures.