Matched Photometric Catalogs of GALEX UV Sources with Gaia DR2 and SDSS DR14 Databases (GUVmatch)

We have matched the ultraviolet (UV) sources in GUVcat_AIS with optical databases that have similar depth and wide sky coverage. GUVcat_AIS has Galaxy Evolution Explorer (GALEX) far-UV (FUV, λ_eff ∼ 1528 Å) and near-UV (NUV, λ_eff ∼ 2310 Å) photometry of ≈83 million sources, covering 24,788 square degrees of the sky, with a typical depth of FUV = 19.9 and NUV = 20.8 AB mag. Matches with Gaia and the Sloan Digital Sky Survey (SDSS) databases are presented here. Gaia data release 2 (DR2), covering the entire GUVcat footprint, detected about one-third of the GUVcat_AIS sources. We found 31,925,294 Gaia DR2 counterparts to 30,024,791 GUVcat_AIS unique sources, with photometry in the Gaia G band and often also in Gaia BP and RP bands; 26,275,572 matches have a parallax measurement, 21,084,628, 18,588,140, and 16,357,505 have a parallax error less than 50%, 30%, and 20%, respectively. The match with SDSS data release 14 (DR14) yields 23,310,532 counterparts to 22,207,563 unique GUVcat_AIS sources, 10,167,460 of which are pointlike, over a total overlap area of ≈11,100 square degrees (Bianchi et al. 2019). SDSS adds five optical magnitudes to the UV photometry : u, g, r, i, z, and optical spectra of 860,224 matched sources. We used a match radius of 3″, consistent with previous works, although the positions agree to ≲1"5 for the majority of (pointlike) matched sources, in order to identify possible multiple matches whose UV flux could be unresolved in GALEX imaging. The catalogs can be trimmed to a tighter match radius using the provided separation. The multiband photometry is used to identify classes of astrophysical objects that are prominent in UV, to characterize the content of the GUVmatch catalogs, where stars in different evolutionary stages, quasi-stellar objects, and galaxies can be separated.