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Differences between GALEX source catalogs

jhargisjhargis Member, Administrator, Institute_Staff, Moderator_MAST, Admin_MAST Posts: 30 admin
edited May 2016 in GALEX
What are the difference between the various source catalogs?


  • scflemingscfleming Member, Institute_Staff, Moderator_MAST, Admin_MAST Posts: 35
    The source catalog produced by the mission is referred to as the "MCAT". The MCAT was created by running source extraction on the FUV and NUV images separately, then merging them together into a merged catalog. A version for each "visit" as well as a version for a single "coadd" of each field is produced. Other catalogs are created by community members and archived at MAST as High Level Science Products. These include the "GCAT" and "BCSCAT", which are unique source catalogs that attempt to eliminate duplicate source measurements when objects are observed more than once. They choose the deepest (highest signal-to-noise) flux measurement available for each source. The creation of these catalogs differ from the MCAT creation process, although both rely on the MCAT as starting points. For instance, the GCAT performs forced photometry on the FUV images at the NUV source positions. You can read more about the GCAT and BCSCAT at and
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