4.5.10 Astronomical checks of the data

Author(s): Uli Bastian

In addition to the above-mentioned direct comparison with ground-based astrometry, other prior consensus knowledge on distances and motions of stars was used to verify/validate the Gaia DR3 astrometry. Among the source classes and criteria used for this purpose are:

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  LMC & SMC members as a (regional) check on the parallax zeropoint

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  quasars as a (global) check on the parallax zeropoint

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  distant Cepheids and RR Lyrae stars as a (global) check on the parallax zeropoint

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  quasar positions as check against the ICRF (as mentioned above already)

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  quasars as a check on proper-motion precision at the faint end

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  stellar aggregates (LMC, SMC, star clusters) as a check on proper-motion precision at the bright end

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  stellar aggregates as check on colour- and magnitude-dependent biases

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  negative-parallaxes tail as check on parallax precision and outlier distribution

Results are given in the Gaia DR3 astrometry paper, (Lindegren et al. 2021b) and in the Gaia DR3 validation paper (Fabricius et al. 2021). The parallax zeropoint, or more precisely the parallax bias for both the five- and six-parameters solutions as a function of several variables is discussed in Lindegren et al. (2021a), which provides a tentative recipe for the correction of Gaia DR3 parallaxes.