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Abstract Reference: 31003
Identifier: P1.35
Presentation: Poster presentation
Key Theme: 1 Reduction and Analysis Algorithms for Large Databases and Vice-versa

Cross-matching the Chandra Source Catalog

Authors:
Rots Arnold, Burke Douglas, Civano Francesca, Hain Roger, Nguyen Dan

Cross-matching against the Chandra Source Catalog (CSC) presents special challenges, since the Point Spread Function (PSF) of the Chandra X-ray Observatory varies considerably over the field of view. This is not only a significant problem when cross-matching against other catalogs, but also in cross-matching source detections from overlapping Chandra observations. Among the source parameters in Release 2 of the CSC are error ellipses for their positions, as well as PSF ellipses. We developed a cross-match tool that is based on the Bayesian algorithms  by Budavari, Heinis, and Szalay (ApJ 679, 301 and 705, 739), making use of the error ellipses. However, we ran into two major issues: calculating match probabilities only on the basis of error ellipses breaks down when the PSFs are significantly different; and the number of matches to be considered increases alarmingly when the number of catalogs involved in the match is more than just a handful. To counter this we made modifications in the algorithm and the procedure, respectively which we will represent, accompanied by examples of intra-CSC cross-match results. This work has been supported by NASA under contract NAS 8-03060 to the Smithsonian Astrophysical Observatory for operation of the Chandra X-ray Center. It depends critically on the services provided by the ADS.