Veritas in Duo Sigma--Look at All Those Sources!
Session 6 -- Miscellaneous
Display presentation, Wednesday, January 12, 9:30-6:45, Salons I/II Room (Crystal Gateway)

## [6.06] Veritas in Duo Sigma--Look at All Those Sources!

D.J. Helfand, E.C. Moran, and B. Oppenheimer (Columbia U.), R.H. Becker (UC Davis and LLNL), R.L. White (STScI)

We present the final source catalogs derived from the Columbia {\sl Einstein\/} IPC database. By taking advantage of our flat-fielding and editing techniques, as well as employing variable-aperture detection algorithms and relaxing the sociologically determined detection threshold, we have detected and characterized tens of thousands of X-ray sources not included in the standard IPC source catalog which was designed to be a high-reliability list produced from standard data products. For example, the point-source catalog derived from the 2600 one square-degree fields at $\vert b\vert >10^\circ$ (excluding the Magellanic Clouds and other sources of substantial diffuse emission) includes nearly 50,000 entries down to the two-sigma level, a large fraction of which are real X-ray sources. Using the distribution of these sources over the face of the detector, as well as an analysis of the match rate with a variety of radio, optical, and infrared catalogs, we can assign to each source an a posteriori\/ reliability, further enhancing the utility of the catalog. Seperate lists of sources with extreme spectra (e.g., all counts below 1 keV, only detected in the 1.5--3.5 keV band, etc.) are appended. In addition, we have searched for diffuse sources on angular sizes ranging from $2^\prime$ to $12^\prime$, discovering a large number of objects, at least some of which are associated with uncatalogued clusters and groups of galaxies. The implications of these results for the origins of both diffuse Galactic emission and the cosmic X-ray background will be presented.

\medskip \noindent This work was supported by NASA under contract NAS5-32063.