The extended Gaia-PS1-SDSS (GPS1+) proper motion catalog

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 r ∼ 20 mag. In this study, we present GPS1+ the extension GPS1 catalog down to r ∼ 22.5 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 mas yr−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 mas yr−1. 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 mas yr−1; 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 mas yr−1. However, the secondary∼136 million sources only have PS1 astrometry, the average precision is worse than 15.0 mas yr−1. 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 TAP Service.