Towards the ICRF3: astrometric comparison of the USNO 2016A VLBI solution with ICRF2 and Gaia DR1

Abstract

The VLBI USNO 2016A (U16A) solution is part of a work-in-progress effort by USNO towards the preparation of the ICRF3. Most of the astrometric improvement with respect to the ICRF2 is due to the re-observation of the VCS sources. Our objective in this paper is to assess U16A's astrometry. A comparison with ICRF2 shows statistically significant offsets of size 0.1 mas between the two solutions. While Gaia DR1 positions are not precise enough to resolve these offsets, they are found to be significantly closer to U16A than ICRF2. In particular, the trend for typically larger errors for Southern sources in VLBI solutions are decreased in U16A. Overall, the VLBI-Gaia offsets are reduced by 21%. The U16A list includes 718 sources not previously included in ICRF2. Twenty of those new sources have statistically significant radio-optical offsets. In two-thirds of the cases, these offsets can be explained from PanSTARRS images.

arXiv comment14 pages, 10 figures

References in corpus (14)

• HEALPix -- a Framework for High Resolution Discretization, and Fast Analysis of Data Distributed on the Sphere
• The Pan-STARRS1 Surveys
• Gaia Data Release 1: Astrometry - one billion positions, two million proper motions and parallaxes
• The VLBA Calibrator Survey - VCS1
• Analysis of astrometric catalogues with vector spherical harmonics
• VLBI-Gaia offsets favor parsec-scale jet direction in Active Galactic Nuclei
• Gaia Data Release 1: The reference frame and the optical properties of ICRF sources
• On significance of VLBI/Gaia position offsets
• Astrometric evidence for a population of dislodged AGN
• Optical-radio positional offsets for active galactic nuclei
• The local stellar velocity field via vector spherical harmonics
• Radio-Optical Reference Frame Link Using the US Naval Observatory Astrograph and Deep CCD Imaging
• A Global Astrometric Solution for Pan-STARRS referenced to ICRF2
• Cross-validation in nonparametric regression with outliers

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• Precise radio astrometry and new developments for the next generation of instruments
• Dissecting the AGN disk-jet system with joint VLBI-Gaia analysis
• The precious set of radio-optical reference frame objects in the light of Gaia DR2 data
• Systematics and accuracy of VLBI astrometry: What can be learned from a comparison with Gaia Data Release 2
• Comparison of multifrequency positions of extragalactic sources from global geodetic VLBI monitoring program and Gaia EDR3
• Towards a robust estimation of orientation parameters between ICRF and $Gaia$ celestial reference frames
• Metrics of Astrometric Variability in the International Celestial Reference Frame: I. Statistical analysis and selection of the most variable sources