Radio-loud active galaxies in the northern ROSAT All-Sky Survey. I. Radio identifications

We present 5 GHz high resolution VLA observations of 2,127 radio- and X-ray-emitting sources found in both the Green Bank (GB) 5 GHz radio catalog and the ROSAT All-Sky Survey (RASS). We report core flux densities and positions accurate to +/-0.5". Combined with the GB measuremens of the total radio emission, we derive the core-to-lobe ratio of objects in our sample and discuss their core-dominance relative to samples of radio galaxies and BL Lacertae objects. Our results show the ROSAT/GreenBank (RGB) sample is approximately an order of magnitude more core-dominated than the radio galaxy sample, but is more than an order of magnitude less core-dominated than highly beamed BL Lacertae object samples. Using simple beaming models, this indicates the typical object in the RGB catalog exhibits beamed radio emission and is oriented at a modest angle to the line-of-sight (theta ~ 25-30 degrees). The case of the origin of the X-ray emission is not as clear; the data are consistent with either an anisotropic unbeamed or moderately beamed X-ray component.