GALEX GCAT catalogues ===================== This resource contains the GALEX GCAT catalogues: the GALEX All-Sky Source Catalogue (GASC) and the GALEX Medium Imaging Survey Catalogue (GMSC). More information on the GCAT is available on `the Caltech GALEX site`__. In particular: __ http://www.galex.caltech.edu/wiki/GCAT_Manual GALEX has been undertaking a number of surveys covering large areas of sky at a variety of depths. However making use of this large data set can be difficult because the standard GALEX database contains all of the detected sources which include many duplicate observations of the same sources as well as numerous spurious low signal-to-noise sources. At the same time, the sky footprint associated with GALEX observations has not been well defined or presented in an easily useable format. In order to remedy these problems, we have constructed two catalogues of GALEX measurements, namely the GALEX All-Sky Survey Source Catalog (GASC) and the GALEX Medium Imaging Survey Catalog (GMSC). Our intention is that these catalogues will provide the primary reference catalog useful for matching GALEX measurements with other large surveys of the sky at other wavelengths. Covering a total of 26,300 deg2 of sky, the GASC consists of all GALEX observations with exposure times below 800 sec and reaches a depth of NUV 21 (AB mag). The GMSC covers a smaller region of 5000 deg2 with exposure times between 800 and 10,000 sec and reaches a depth of NUV 23 mag. There are a total of 40 million unique sources in the GASC and 22 million in the GMSC. Each catalogues accompanied by exposure time, coverage and flag maps in FITS and Healpix formats. These catalogues do not contain the deepest images available for the GALEX deep fields. While the sky covered by these tiles is included, we have limited the total exposure time to 10,000 sec. Crowding becomes a significant issue for the depths reached in the deep fields and thus requires more careful treatment than what is possible using the standard GALEX pipeline source detection. Users interested in these regions can find the deepest co-adds from the MAST archive and complete their own an analysis. Currently these catalogues only include GALEX data up to the GR6 data release. To identify uniquely a source, one must use the name column. These catalogues were limited to HELP coverage and a ``field`` column has been added. HELP field coverage ------------------- Here is the number of GMSC and GASC sources per HELP field: ================== =============== =============== Field GMSC counts GASC counts ================== =============== =============== AKARI-NEP 6,142 14,563 AKARI-SEP 12,356 7,756 Bootes 61,748 20,059 CDFS-SWIRE 49,905 34,889 COSMOS 40,403 15,662 EGS 21,564 6,259 ELAIS-N1 60,774 28,561 ELAIS-N2 46,681 27,889 ELAIS-S1 39,405 26,354 GAMA-09 262,123 104,706 GAMA-12 219,450 80,206 GAMA-15 269,669 97,722 HDF-N 3,321 1,872 Herschel-Stripe-82 1,318,546 468,385 Lockman-SWIRE 97,661 26,865 HATLAS-NGP 185,199 217,288 SA13 401 HATLAS-SGP 265,261 464,442 SPIRE-NEP 346 SSDF 94,053 227,424 xFLS 36,163 15,790 XMM-13hr 166 XMM-LSS 72,816 36,467 ================== =============== =============== History ------- ======== ============================================================= 20170116 Rename NGP to HATLAS-NGP and SGP to HATLAS-SGP. 20160426 Addition of the GASC catalogue retrieved from STSCI GALEX CasJobs. 20160303 Catalogue retrieved from STSCI GALEX CasJobs and ingested. ======== =============================================================