Revised Catalog of GALEX Ultraviolet Sources. I. The All-Sky Survey: GUVcat_AIS

By L. Bianchi, B. Shiao, D. Thilker. 2017

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The Galaxy Evolution Explorer (GALEX) imaged the sky in two ultraviolet (UV) bands, far-UV (FUV, λeff ∼ 1528 Å), and near-UV (NUV, λeff ∼ 2310 Å), delivering the first comprehensive sky surveys at these wavelengths. The GALEX database contains FUV and NUV images, ∼500 million source measurements and over 100,000 low-resolution UV spectra. The UV surveys are a unique resource for statistical studies of hot stellar objects, z ≲ 2 QSOs, star-forming galaxies, nebulae and the interstellar medium, and provide a roadmap for planning future UV instrumentation and follow-up observing programs. We present science-enhanced, “clean” catalogs of GALEX UV sources, with useful tags to facilitate scientific investigations. The catalogs are an improved and expanded version of our previous catalogs of UV sources (BCScat). With respect to BCScat, we have patched 640 fields for which the pipeline had improperly coadded non-overlapping observations, and we provide a version with a larger sky coverage (about 10%) by relaxing the restriction to the central area of the GALEX field to 1.°1 diameter (GUVcat_AIS_fov055), as well as the cleaner, more restrictive version using only the 1° central portion of each field as in BCScat (GUVcat_AIS_fov050). We added new tags to facilitate selection and cleaning of statistical samples for science applications: we flag sources within the footprint of extended objects (nearby galaxies, stellar clusters) so that these regions can be excluded for estimating source density. As in our previous catalogs, in GUVcat duplicate measurements of the same source are removed, so that each astrophysical object has only one entry. Such a unique-source catalog is needed to study the density and distributions of sources, and to match UV sources with catalogs at other wavelengths. The catalog includes all observations from the All-Sky Imaging Survey (AIS), the survey with the largest area coverage, with both FUV and NUV detectors exposed: over 28,700 fields, made up of a total of 57,000 observations (“visits”). The total area covered, when overlaps are removed and gaps are accounted for, is 24,790 square degrees for GUVcat_AIS_fov055 (GUVcat_AIS_fov055) and 22,125 square degrees for (GUVcat_AIS_fov050). The total numbers of “unique” AIS sources (eliminating duplicate measurements) are 82,992,086 ( ) and 69,772,677 ( ). The typical depth of the GUVcat_AIS catalog is FUV = 19.9, NUV = 20.8 AB mag.

Subfields: Astronomy and Astrophysics, Biomedical Engineering, Instrumentation

View Paper: https://www.semanticscholar.org/paper/af40d5d3f371ea6cd82121490db0a5ce26df7e56

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Illuminating Low Surface Brightness Galaxies with the Hyper Suprime-Cam Survey (2017, background): “…of all individual GALEX visits and checked if the positions fell within the field-of-view radius from the center of any observation, as suggested by Bianchi et al. (2017). give the reader a context from which to view the HSC-SSP images, which push to much lower surface brightness levels than is…”