The Extended Gaia-PS1-SDSS (GPS1+) Proper Motion Catalog

The Gaia + PanSTARRS1 (PS1) + Sloan Digital Sky Survey (SDSS) + Two Micron All-Sky Survey (2MASS) (GPS1) catalog was released in 2017. It delivered precise proper motions for around 350 million sources down to a magnitude of r similar to 20 mag. In this study, we present GPS1+, the extension GPS1 catalog down to r similar to 22.5 mag, based on Gaia data release 2 (DR2), PS1, SDSS, and 2MASS astrometry. GPS1+ totally provides proper motions for similar to 400 million sources with a characteristic systematic error of less than 0.1 mas yr(-1). This catalog is divided into two subsamples, i.e., the primary and secondary parts. The primary similar to 264 million sources have either or both Gaia and SDSS astrometry, with a typical precision of 2.0-5.0 mas yr(-1). In this part, similar to 160 million sources have Gaia proper motions, and 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 similar to 0.1 dex on average; similar to 50 million sources are the objects whose proper motions are missing in Gaia DR2, and we provide their proper motions with a precision of similar to 4.5 mas yr(-1). The remaining similar to 54 million faint sources are beyond Gaia detecting capability, and we provide their proper motions for the first time with a precision of 7.0 mas yr(-1). However, the secondary similar to 136 million sources only have PS1 astrometry, where the average precision is worse than 15.0 mas yr(-1). The large uncertainty probably limits it to qualitative applications. All the proper motions have been validated using QSOs and the existing Gaia proper motions. The catalog will be available via the TAP Service in the German Astrophysical Virtual Observatory.