An infrared celestial reference frame realized by the CatWISE2020 catalog

Context. The International Celestial Reference System (ICRS) is currently realized by radio (ICRF3) and optical (Gaia-CRF3) reference frames, while an infrared reference frame is still missing. Aims. We aim to establish an infrared celestial reference frame using the CatWISE2020 catalog and investigate its alignment with Gaia DR3 data. Methods. We cross-matched 1.89 billion CatWISE2020 sources with Gaia DR3 and Gaia-CRF3 sources from five- or six-parameter astrometric solutions. We performed a vector-spherical-harmonics (VSH) analysis on positional and proper-motion differences for common sources. Results. The global rotation and glide between CatWISE2020 and Gaia DR3 are found to be 6.6 and 6.9 mas for position system, and 1.9 and 2.7 mas yr−1 for proper motion system. Internal differences between stellar frame and extragalactic frame in CatWISE2020 are found to be ~6 mas for position and ~1 mas yr−1 for proper motion. Magnitude-dependent systematic differences on positions and proper motions are also presented. Conclusions. So far, the CatWISE2020 catalog is the best available comprehensive infrared all-sky survey with the highest astrometric accuracy. After correcting for systematic errors with respect to the Gaia celestial reference frame, it can serve as an infrared realization of the ICRS.