Improvements to Pan-STARRS1 Astrometry Using Gaia

TL;DR

This paper enhances the astrometric accuracy of the Pan-STARRS1 catalog by leveraging Gaia DR2 data, applying a correction algorithm that significantly reduces positional and proper motion residuals for a vast number of objects.

Contribution

The authors develop and implement a spatially adaptive correction algorithm that improves Pan-STARRS1 astrometry using Gaia DR2, reducing residuals by about one-third.

Findings

Residual positional errors are reduced by 33% for point-like objects.

Proper motion residuals are decreased by 24%.

Residual errors vary with object morphology, magnitude, and observational conditions.

Abstract

We use the Gaia DR2 catalog to improve the astrometric accuracy of about 1.7 billion objects in Pan-STARRS1 Data Release 2 (PS1 DR2). We also obtain proper motions for these PS1 objects. The cross match between Gaia and PS1 reveals residuals that are correlated on a scale of about 1 arcmin. We apply a spatially adaptive correction algorithm for all PS1 objects having more than two detections to reduce these residuals and align the object positions to Gaia. For point-like PS1 objects that cross match to Gaia, the algorithm reduces PS1/Gaia residuals by 33% in position (median value of 13.5 mas reduced to 9.0 mas) and by 24% in proper motion (median value of 6.3 mas/yr reduced to 4.8 mas/yr). The residuals for the corrected positions are smallest for objects with the most point-like morphologies and with intermediate magnitudes of about 17 mag. The residual errors in declination are systematically larger than those in right ascension; the declination errors increase with zenith angle in proportion to the air mass of the observations. Declination positional residuals at a given declination generally vary with color and are consistent with the effects of differential atmospheric refraction. In principle, these residuals could be reduced further by taking into account object color.