Identifying quasars with astrometric and mid-infrared methods from APOP
  and ALLWISE
  Context. Quasars are spatially stationary, and they are essential objects in
astrometry when defining reference frames. However, the census of quasars is
far from complete. Mid-infared colors can be used to find quasar candidates
because AGNs show a peculiar appearance in mid-infrared color, but these
methods are incapable of separating quasars from AGNs. Aims. The aim of our
study is to use astrometric and mid-infrared methods to select quasars and get
a reliable quasar candidates catalog. Methods. We used a near-zero proper
motion criterion in conjuction with WISE (all-sky Wide-field Infrared Survey
Explorer) [W1-W2] color to select quasar candidates. The [W1-W2] color
criterion is defined by the linear boundary of two samples: LAMOST DR5 quasars,
which serve as the quasar sample, and LAMOST DR5 stars and galaxies, which
serve as the non-quasar sample. The contamination and completeness are
evaluated. Results. We present a catalog of 662 753 quasar candidates, with a
completeness of about 75% and a reliability of 77.2%.
