VEXAS: the VISTA EXtension to Auxiliary Surveys -- Data Release 1: the
  Southern Galactic Hemisphere
  We present the first public data release of the VISTA EXtension to Auxiliary
Surveys (VEXAS), comprising of 9 cross-matched multi-wavelength photometric
catalogs where each object has a match in at least two surveys. We aim at a
spatial coverage as uniform as possible in the multi-wavelength sky, with the
purpose of providing the astronomical community with reference magnitudes and
colours for various scientific uses, including: object classification (e.g.
quasars, galaxies, and stars; high-z galaxies, white dwarfs, etc.); photometric
redshifts of large galaxy samples; searches of exotic objects such as, for
example, extremely red objects and lensed quasars. We have cross-matched the
wide-field VISTA catalogs (the VISTA Hemisphere Survey and the VISTA Kilo
Degree Infrared Galaxy Survey) with the AllWISE mid-infrared Survey, requiring
that a match exists within 10 arcsec. We have further matched this table with
X-Ray and radio data (ROSAT, XMM, SUMSS). We also performed a second
cross-match between VISTA and AllWISE, with a smaller matching radius (3"),
including WISE magnitudes. We have then cross-matched this resulting table
($\approx138\times10^6$ objects) with three photometric wide-sky optical deep
surveys (DES, SkyMapper, PanSTARRS). We finally include matches to objects with
spectroscopic follow-up by the SDSS and 6dFGS. To demonstrate the power of
all-sky multi-wavelength cross-match tables, we show two examples of scientific
applications of VEXAS, in particular using the publicly released tables to
discover strong gravitational lenses (beyond the reach of previous searches),
and to build a statistically large sample of extremely red objects. The VEXAS
catalog is currently the widest and deepest, public, optical-to-IR photometric
and spectroscopic database in the Southern Hemisphere.
