A Gaia DR2 Mock Stellar Catalog
  We present a mock catalog of Milky Way stars, matching in volume and depth
the content of the Gaia data release 2 (GDR2). We generated our catalog using
Galaxia, a tool to sample stars from a Besancon Galactic model, together with a
realistic 3D dust extinction map. The catalog mimicks the complete GDR2 data
model and contains most of the entries in the Gaia source catalog: 5-parameter
astrometry, 3-band photometry, radial velocities, stellar parameters, and
associated scaled nominal uncertainty estimates. In addition, we supplemented
the catalog with extinctions and photometry for non-Gaia bands. This catalog
can be used to prepare GDR2 queries in a realistic runtime environment, and it
can serve as a Galactic model against which to compare the actual GDR2 data in
the space of observables. The catalog is hosted through the virtual observatory
GAVO's Heidelberg data center service and thus can be queried using ADQL as for
GDR2 data.
