An infrared celestial reference frame realized by the CatWISE2020 catalog

Zhen-Wei Wang, Jia-Cheng Liu, Niu Liu, Zi Zhu, Jun Yao, Ibnu Nurul Huda, Xia-Xuan Zhang, Hua-Feng Yu

December 2025

Coordinate (left) and proper-motion (right) offsets between CatWISE2020 and Gaia DR3.

Abstract

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 $2.7,\mathrm{mas,yr^{-1}}$ for proper motion system. Internal differences between stellar frame and extragalactic frame in CatWISE2020 are found to be approximately 6 mas for position and approximately $1,\mathrm{mas,yr^{-1}}$ 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.

Type

Journal article

Publication

Astronomy & Astrophysics, 704, A136

An infrared extension of the celestial reference frame

The International Celestial Reference System is currently realized primarily in the radio and optical bands. An infrared realization would extend its wavelength coverage and provide a denser reference grid in regions affected by strong interstellar extinction, such as the Galactic plane and bulge.

In this study, we cross-matched CatWISE2020 with Gaia DR3, identifying approximately 404 million common sources, including 1.38 million Gaia-CRF3 quasars. We investigated their positional and proper-motion differences using vector spherical harmonics, with separate analyses for stellar and extragalactic sources.

Main results

Large-scale systematic offsets: For stellar sources, the rotation and glide amplitudes relative to Gaia DR3 are approximately 6.6 and 6.9 mas in position, and 1.9 and $2.7,\mathrm{mas,yr^{-1}}$ in proper motion.
Internal frame differences: The stellar and extragalactic reference frames within CatWISE2020 differ by approximately 6 mas in position and $1,\mathrm{mas,yr^{-1}}$ in proper motion.
Magnitude-dependent systematics: The offsets vary significantly with magnitude, indicating that a single global correction cannot fully describe the systematic differences. No significant color dependence was found.
Underestimated uncertainties: The reported positional uncertainties are underestimated by factors of approximately 1.5–2.5.

The featured figure illustrates the spatial distribution of the positional and proper-motion offsets. Averaging the offsets within 192 equal-area sky pixels reveals coherent patterns, demonstrating the need to account for large-scale systematics when linking CatWISE2020 to Gaia.

Implications

After correcting systematic offsets relative to Gaia, CatWISE2020 can serve as an infrared realization of the ICRS. Its deeper coverage and improved proper motions offer substantial advantages over AllWISE. However, global corrections do not remove all tile-dependent systematics, and the comparatively large proper-motion uncertainties limit the long-term stability of the frame. Further improvements will require refined calibration and, ultimately, higher-precision infrared astrometry.