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 (23σ) and will limit the anisotropy of the Hubble expansion to about 2%.
@article{arxiv.1804.02064,
title = {The Gaia-WISE Extragalactic Astrometric Catalog},
author = {Jennie Paine and Jeremy Darling and Alexandra Truebenbach},
journal= {arXiv preprint arXiv:1804.02064},
year = {2018}
}