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Session 19 - Source Surveys, Galaxy Surveys, Distance Scale II.
Display session, Wednesday, January 07
We present the results of the correlation of the ROSAT All-Sky Survey (RASS) and FIRST catalogs. The RASS catalog consists of \sim80,000 soft X-ray sources with fluxes \ge1-5\times10^-13\,erg\,s^-1\,cm^-2 and the FIRST (Faint Images of the Radio Sky at Twenty centimeters) catalog currently consists of \sim250,000 sources \ge1\,mJy over 5,000\,deg^-2 of the high Galactic latitude sky. While counterparts to many X-ray sources are easily identified with single radio sources, we find that 40% of the X-ray sources in the correlation have more than one plausible radio counterpart. Many of these sources are radio doubles and triples exhibiting not only a core and lobes, but often highly complex radio morphologies. Other X-ray fields which contain multiple faint radio sources are likely associated with clusters.
The FIRST catalog also provides excellent positions (\le1^\prime\prime) which enables unambiguous identification of optical counterparts which were chosen from Automatic Plate Machine (APM) scans of the POSS\,I photographic plates. We will discuss particularly those cases where the radio morphology is complex.
While some nearby galaxies and stars are detected, the majority of these sources are AGN, including Broad and Narrow-line radio galaxies, BL Lacs, Seyferts and quasars. Because of the low radio flux density limit of the FIRST survey, many objects are radio-quiet even though they are radio- (and X-ray-) selected. Finally, we discuss the broadband radio, optical and X-ray spectral energy distribution of all identified sources and the transitions between various spectroscopic classes.
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