The Southern Proper Motion Program IV. The SPM4 Catalog

TL;DR

The SPM4 catalog provides comprehensive proper motions, positions, and photometry for over 103 million stars and galaxies in the southern sky, improving astrometric data quality and coverage.

Contribution

This paper introduces the fourth installment of the SPM catalog, offering enhanced data for southern sky astrometry based on photographic and CCD observations.

Findings

Proper-motion precision of 2-3 mas/yr for well-measured stars

Coverage of over 103 million stars and galaxies

Systematic uncertainties around 1 mas/yr

Abstract

We present the fourth installment of the Yale/San Juan Southern Proper Motion Catalog, SPM4. The SPM4 contains absolute proper motions, celestial coordinates, and (B,V) photometry for over 103 million stars and galaxies between the south celestial pole and -20 deg declination. The catalog is roughly complete to V=17.5 and is based on photographic and CCD observations taken with the Yale Southern Observatory's double-astrograph at Cesco Observatory in El Leoncito, Argentina. The proper-motion precision, for well-measured stars, is estimated to be 2 to 3 mas/yr, depending on the type of second-epoch material. At the bright end, proper motions are on the International Celestial Reference System by way of Hipparcos Catalog stars, while the faint end is anchored to the inertial system using external galaxies. Systematic uncertainties in the absolute proper motions are on the order of 1 mas/yr.