The Property of the Gaia Celestial Reference Frame 3 (Gaia-CRF3)

Abstract

With the release of Gaia DR3, evaluating the performance and consistency of its reference frame (Gaia-CRF3) with the International Celestial Reference Frame (ICRF3) has become a critical task. Gaia-CRF3 serves as the second non-rotating inertial reference frame in the optical wavelength for the implementation of the International Celestial Reference System (ICRS). This study assesses the properties of Gaia-CRF3 by uniformly sampling Active Galactic Nuclei (AGN) sources from Gaia DR3 using two methods: Fibonacci grid sampling and HEALPix pixel sampling. Both techniques aim to create an all-sky uniformly distributed star catalog to minimize correlations between Vector Spherical Harmonic (VSH) expansion coefficients. Using the Fibonacci grid, approximately 430,000 uniformly distributed sources were selected from the 5-parameter solution of Gaia DR3. After VSH processing, the rotation vector and glide vector were determined as R=(10.7±3.1,2.2±2.7,‑2.5±4.0)μas · year^‑1 and G=(0.3±3.1,‑1.2±2.7,‑2.5±4.0)μas · year^‑1, respectively. Using HEALPix sampling, a catalog of approximately 190,000 sources was created by averaging source positions within each pixel. The VSH analysis yielded R=(11.7±2.1,2.7±1.8,‑3.7±2.7)μas · year^‑1 and G=(0.9±2.1,‑2.3±1.8,‑4.4±2.7)μas · year^‑1. Comparison with results derived from a non-uniformly sampled catalog showed that uniform sampling significantly reduced both the magnitudes of the R and G components and their associated errors. The derived values for Gaia-CRF3 are consistent with ICRF3, whose rotation and glide vectors are R=(‑3.44±0.30,+1.57±0.28,‑1.24±0.32)μas · year^‑1 and G=(+3.41±6.71,+8.99±6.50,‑1.47±6.04)μas · year^‑1. These findings confirm that Gaia-CRF3 is a reliable and accurate reference frame, comparable in precision to ICRF3, making it a robust implementation of the optical ICRS for astrometric applications.