GaiaData Release 3

Abstract

Context.GaiaData Release 3 (GaiaDR3) contains the second release of the combined radial velocities. It is based on the spectra collected during the first 34 months of the nominal mission. The longer time baseline and the improvements of the pipeline made it possible to push the processing limit fromGRVS = 12 inGaiaDR2 toGRVS = 14 mag.Aims.We describe the new functionalities implemented forGaiaDR3, the quality filters applied during processing and post-processing, and the properties and performance of the published velocities.Methods.ForGaiaDR3, several functionalities were upgraded or added to the spectroscopic pipeline. The calibrations were improved in order to better model the temporal evolution of the straylight and of the instrumental point spread function (PSF). The overlapped spectra, which were mostly discarded inGaiaDR2, are now handled by a dedicated module. The hot star template mismatch, which prevented publication of hot stars inGaiaDR2, is largely mitigated now, down toGRVS = 12 mag. The combined radial velocity of stars brighter than or equal toGRVS = 12 mag is calculated in the same way as inGaiaDR2, that is, as the median of the epoch radial velocity time series. The combined radial velocity of the fainter stars is measured from the average of the cross-correlation functions.Results.GaiaDR3 contains the combined radial velocities of 33 812 183 stars. With respect toGaiaDR2, the temperature interval has been expanded fromTeff ∈ [3600, 6750] K toTeff ∈ [3100, 14 500] K for the bright stars (GRVS ≤ 12 mag) and [3100, 6750] K for the fainter stars. The radial velocities sample a significant part of the Milky Way: they reach a few kiloparsecs beyond the Galactic centre in the disc and up to about 10−15 kpc vertically into the inner halo. The median formal precision of the velocities is 1.3 km s−1atGRVS = 12 and 6.4 km s−1atGRVS = 14 mag. The velocity zeropoint exhibits a small systematic trend with magnitude that starts aroundGRVS = 11 mag and reaches about 400 m s−1atGRVS = 14 mag. A correction formula is provided that can be applied to the published data. TheGaiaDR3 velocity scale agrees satisfactorily with APOGEE, GALAH, GES, and RAVE; the systematic differences mostly remain below a few hundred m s−1. The properties of the radial velocities are also illustrated with specific objects: open clusters, globular clusters, and the Large Magellanic Cloud. For example, the precision of the data allows mapping the line-of-sight rotational velocities of the globular cluster 47 Tuc and of the Large Magellanic Cloud.