ARXA is now superseded. The up-to-date catalog is the Million
Optical - Radio/X-ray Associations (MORX, 2016 PASA accepted) catalog, available here
These are 602,570 optical objects which are associated to radio/X-ray detections from the NVSS, FIRST, SUMSS, XMM-Newton, Chandra, or ROSAT RASS, PSPC, HRI and WGA survey catalogs. All association detections are shown, across all these catalogs. Also displayed: the calculated probability that the optical object is in turn a quasar, galaxy, star, or erroneous association. The optical object is identified from the literature, if known.
Here is the ReadMe and pre-publication paper. Quick browse of sample data here.
Get the file (20 Mb zipped) here: download ATLAS-of-ASSOCIATIONS.zip
Eric Flesch, last updated 20 September 2016