Radio and X-ray bright AGN: the ROSAT-FIRST correlation

We present the results of a correlation of the ROSAT All-Sky Survey with th e April 1997 release of the VLA 20cm FIRST catalogue. We focus our analysis on the 843 X-ray sources which have unique radio counterparts. The majorit y of these objects (84%) have optical counterparts on the POSS 1 plates. Ap proximately 30% have been previously classified and we obtain new spectrosc opic classifications for 85 sources by comparison with the ongoing FIRST Br ight Quasar Survey and 106 additional sources from our own new spectroscopi c data. Approximately 51% of the sources are presently classified, and the majority of the unclassified objects are optically faint. The newly classif ied sources are generally radio weak, exhibiting properties intermediate wi th previous samples of radio- and Xray-selected AGN. This also holds for th e subsample of 71 BL Lacs which includes many intermediate objects. The 146 quasars show no evidence for a bimodal distribution in their radio-loudnes s parameter, indicating that the supposed division between radio-quiet and radio-loud AGN may not be real. The X-ray and radio luminosities are correl ated over two decades in radio luminosity, spanning the radio-loud and radi o-quiet regimes, with radio-quiet quasars showing a linear correlation betw een the two luminosities. Many of the sources show peculiar or unusual prop erties which call for more detailed follow-up observations. We also give th e X-ray and radio data for the 518 X-ray sources for which more than one ra dio object is found. Because of the difficulties inherent in identifying op tical counterparts to these complex sources, we do not consider these data in the current analysis(1).