Identifying quasars with astrometric and mid-infrared methods from APOP and ALLWISE

TL;DR

This study combines astrometric proper motion data with mid-infrared color criteria from WISE to efficiently identify a large catalog of quasar candidates, improving completeness and reliability over previous methods.

Contribution

It introduces a novel selection method using near-zero proper motion and WISE [W1-W2] color to compile a comprehensive quasar candidate catalog.

Findings

Catalog of 662,753 quasar candidates produced

Completeness of approximately 75% achieved

Reliability of 77.2% demonstrated

Abstract

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%.