The AllWISE Catalog as an Infrared Celestial Reference Frame in the Gaia Era

Abstract The launch of Gaia in 2013 December ushered in a new era of space astrometry, allowing for fundamental reference research at an unprecedented level of precision. The international celestial reference frames in the radio band and the Gaia celestial reference frame in the optical band have been established and are consistent within several microarcseconds for axes orientation. To bridge the gap between the visual and radio bands, an infrared reference frame should be investigated. We present a study aimed at constructing an infrared reference frame using the observations from the AllWISE catalog. It is compared with Gaia DR3 for approximately 0.57 million extragalactic sources and for a full set of 273 million sources. Systematic differences in positions and proper motions, such as magnitude or color equations and vector spherical harmonics, are derived. These systematic differences are comparable to the random errors of AllWISE measurements and can be used to improve the AllWISE source positions and proper motions, making the AllWISE catalog a valuable all-sky reference frame in the infrared band. Our investigation of the AllWISE catalog reveals that extragalactic sources and stars exhibit different astrometric properties. The global difference between the extragalactic source reference frame and the stellar reference frames is found to be 8.6 mas and 13.7 mas for global rotation and glide amplitudes, respectively. Such internal inconsistency should be considered when using AllWISE as an infrared reference frame. Finally, we determine the orientation of the mean Galactic plane using the calibrated source distribution of the AllWISE catalog.