The Gaia-WISE Extragalactic Astrometric Catalog

TL;DR

This paper introduces a comprehensive all-sky AGN catalog derived from Gaia and WISE data, enabling precise measurements of cosmic proper motions and anisotropies with high significance.

Contribution

It provides the first uniform, all-sky AGN catalog from Gaia and WISE, optimized for detecting low-multipole proper motion signals related to cosmic phenomena.

Findings

Catalog contains 567,721 AGN with uniform sky coverage.

Expected Gaia proper motions will detect secular aberration drift at 23σ.

Will constrain Hubble expansion anisotropy to about 2%.

Abstract

The Gaia mission has detected a large number of active galactic nuclei (AGN) and galaxies, but these objects must be identified among the 1000-fold more numerous stars. Extant astrometric AGN catalogs do not have the uniform sky coverage required to detect and characterize the all-sky low-multipole proper motion signals produced by the barycenter motion, gravitational waves, and cosmological effects. To remedy this, we present an all-sky sample of 567,721 AGN in Gaia Data Release 1, selected using WISE two-color criteria. The catalog has fairly uniform sky coverage beyond the Galactic plane, with a mean density of 12.8 AGN per square degree. The objects have magnitudes ranging from $G=8.8$ down to Gaia's magnitude limit, $G=20.7$. The catalog is approximately 50% complete but suffers from low stellar contamination, roughly 0.2%. We predict that the end-of-mission Gaia proper motions for this catalog will enable detection of the secular aberration drift to high significance (23$\sigma$) and will limit the anisotropy of the Hubble expansion to about 2%.