The extended Gaia-PS1-SDSS (GPS1+) proper motion catalog
Abstract
The GPS1 catalog was released in 2017. It delivered precise proper motions for around 350 million sources across three-fourths of the sky down to a magnitude of r20\,mag. In this study, we present GPS1+ the extension GPS1 catalog down to r22.5\,mag, based on Gaia DR2, PS1, SDSS and 2MASS astrometry. The GPS1+ totally provides proper motions for 400 million sources with a characteristic systematic error of less than 0.1. This catalog is divided into two sub-samples, i.e., the primary and secondary parts. The primary 264 million sources have either or both of the Gaia and SDSS astrometry, with a typical precision of 2.0-5.0 . In this part, 160 million sources have Gaia proper motions, we provide another new proper motion for each of them by building a Bayesian model. Relative to Gaia's values, the precision is improved by 0.1\,dex on average at the faint end; 50 million sources are the objects whose proper motions are missing in Gaia DR2, we provide their proper motion with a precision of 4.5; the remaining 54 million faint sources are beyond Gaia detecting capability, we provide their proper motions for the first time with a precision of 7.0 . However, the secondary 136 million sources only have PS1 astrometry, the average precision is worse than 15.0 . All the proper motions have been validated using QSOs and the existing Gaia proper motions. The catalog will be released on-line and available via the VO-TAP Service, or via the National Astronomical Data Center serviced by China-VO: https://nadc.china-vo.org/data/data/gps1p/f.