ESA Science & Technology - Gaia-PS1-SDSS (GPS1) proper motion catalog across 3pi sky

Publication date: 18 March 2017

Authors: Tian, H.-J., et al.

Journal: Preprint; submitted to ApJS

We combine Gaia DR1, PS1, SDSS and 2MASS astrometry to measure proper motions for 350 million sources across three-fourths of the sky down to a magnitude of m_r~20. Using positions of galaxies from PS1, we build a common reference frame for the multi-epoch PS1, single-epoch SDSS and 2MASS data, and calibrate the data in small angular patches to this frame. As the Gaia DR1 excludes resolved galaxy images, we choose a different approach to calibrate Gaia DR1 positions to this reference frame: we exploit the fact that the proper motions of stars in these patches are linear. By simultaneously fitting the positions of stars at different epochs -- Gaia DR1, PS1, SDSS, and 2MASS -- we construct an extensive catalog of proper motions, dubbed GPS1. GPS1 has a characteristic systematic error of less than 0.3 mas yr^-1, and a typical precision of 1.5-2.0 mas yr^-1. The proper motions have been validated using galaxies, open clusters, distant giant stars and QSOs. In comparison with other published faint proper motion catalogs, GPS1's systematic error (<0.3 mas yr^-1) is $\sim$ 10 times better than that of PPMXL and UCAC4 (>2.0 mas yr^-1). Similarly, its precision (~1.5 mas yr^-1) is an improvement by $\sim$ 4 times relative to PPMXL and UCAC4 (~6.0 mas yr^-1). For QSOs, the precision of GPS1 is found to be worse (~2.0-3.0 mas yr^-1), possibly due to their particular differential chromatic refraction (DCR). The catalog will be released on-line and available via the VizieR Service.