Matched photometric catalogs of GALEX UV sources with Gaia DR2 and SDSS DR14 databases (GUVmatch)
Abstract
We have matched the ultraviolet (UV) sources in GUVcatAIS (Bianchi et al.2017) with optical databases having similar depth and wide sky coverage. GUVcatAIS has GALEX far-UV (FUV, lambda-eff ~1528 ) and near-UV (NUV, lambda-eff ~2310) photometry of approx 83~million sources, covering 24,788 square degrees of the sky, with typical depth of FUV=19.9, NUV=20.8~ABmag. Matches with Gaia and SDSS databases are presented here. Gaia data release 2 (DR2), covering the entire GUVcat footprint (Bianchi et al. 2019), detected about one third of the GUVcat\AIS sources. We found 31,925,294 Gaia~DR2 counterparts to 30,024,791 GUVcatAIS unique sources, with photometry in Gaia~G band, and often also in Gaia~BP and RP bands; 26,275,572 matches have a parallax measurement, 21,084,628/18,588,140/16,357,505 with parallax error less than 50%/30%/20%. The match with SDSS data release 14 (DR14) yields 23,310,532 counterparts to 22,207,563 unique GUVcatAIS sources, 10,167,460 of which are point-like, over a total overlap area of ≈11,100~square~degrees (Bianchi et al. 2019). SDSS adds to the UV photometry five optical magnitudes: u,g,r,i,z, and optical spectra of 860,224 matched sources. We used a match radius of 3arcsec, consistent with previous works (e.g., Bianchi et al. 2011a), although the positions agree to 1.5arcsec for the majority of [point-like] 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 multi-band photometry is used to identify classes of astrophysical objects that are prominent in UV, to characterise the content of the GUVmatch catalogs, where stars in different evolutionary stages, QSOs, and galaxies can be separated.