Gaia Data Release 3

Properties and validation of the radial velocities

¹ GEPI, Observatoire de Paris, Université PSL, CNRS, 5 Place Jules Janssen, 92190 Meudon, France
² CNES Centre Spatial de Toulouse, 18 Avenue Edouard Belin, 31401 Toulouse Cedex 9, France
³ Mullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking, Surrey RH5 6NT, UK
⁴ Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Lagrange UMR 7293, CS 34229, 06304 Nice Cedex 4, France
⁵ Royal Observatory of Belgium, Ringlaan 3, 1180 Brussels, Belgium
⁶ Observatoire Astronomique de Strasbourg, Université de Strasbourg, CNRS, UMR 7550, 11 Rue de l’Université, 67000 Strasbourg, France
⁷ Unidad de Astronomía, Fac. Cs. Básicas, Universidad de Antofagasta, Avda. U. de Antofagasta, 02800 Antofagasta, Chile
⁸ CRAAG – Centre de Recherche en Astronomie, Astrophysique et Géophysique, Route de l’Observatoire Bp 63, Bouzareah, 16340 Alger, Algeria
⁹ Institut d’Astrophysique et de Géophysique, Université de Liège, 19c, Allée du 6 Août, 4000 Liège, Belgium
¹⁰ Universiteit Antwerpen, Onderzoeksgroep Toegepaste Wiskunde, Middelheimlaan 1, 2020 Antwerpen, Belgium
¹¹ F.R.S.-FNRS, Rue d’Egmont 5, 1000 Brussels, Belgium
¹² Leibniz Institute for Astrophysics Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany
¹³ Laboratoire Univers et Particules de Montpellier, Université Montpellier, CNRS, Place Eugène Bataillon, CC72, 34095 Montpellier Cedex 05, France
¹⁴ Astronomical Institute, Faculty of Mathematics and Physics, Charles University, V Holešovičkách 2, 180 00 Praha 8, Czech Republic
¹⁵ Laboratoire d’Astrophysique de Bordeaux, Université de Bordeaux, CNRS, B18N, Allée Geoffroy Saint-Hilaire, 33615 Pessac, France
¹⁶ Faculty of Mathematics and Physics, University of Ljubljana, Jadranska ulica 19, 1000 Ljubljana, Slovenia
¹⁷ Institut de Ciències del Cosmos, Universitat de Barcelona (IEEC-UB), Martí i Franquès 1, 08028 Barcelona, Spain
¹⁸ Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
¹⁹ ATOS for CNES Centre Spatial de Toulouse, 18 Avenue Edouard Belin, 31401 Toulouse Cedex 9, France
²⁰ Max Planck Institute for Extraterrestrial Physics, High Energy Group, Gießenbachstraße, 85741 Garching, Germany
²¹ Thales Services for CNES Centre Spatial de Toulouse, 18 Avenue Edouard Belin, 31401 Toulouse Cedex 9, France
²² Department of Astronomy and Theoretical Physics, Lund Observatory, Box 43, 221 00 Lund, Sweden
²³ Telespazio UK S.L. for European Space Agency (ESA), Camino bajo del Castillo s/n, Urbanizacion Villafranca del Castillo, Villanueva de la Cañada, 28692 Madrid, Spain
²⁴ Sorbonne Université CNRS, UMR 7095, Institut d’Astrophysique de Paris, 75014 Paris, France

Received: 8 June 2022
Accepted: 24 October 2022

Abstract

Context. Gaia Data Release 3 (Gaia DR3) 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 from G_RVS = 12 in Gaia DR2 to G_RVS = 14 mag.

Aims. We describe the new functionalities implemented for Gaia DR3, the quality filters applied during processing and post-processing, and the properties and performance of the published velocities.

Methods. For Gaia DR3, 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 in Gaia DR2, are now handled by a dedicated module. The hot star template mismatch, which prevented publication of hot stars in Gaia DR2, is largely mitigated now, down to G_RVS = 12 mag. The combined radial velocity of stars brighter than or equal to G_RVS = 12 mag is calculated in the same way as in Gaia DR2, 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. Gaia DR3 contains the combined radial velocities of 33 812 183 stars. With respect to Gaia DR2, the temperature interval has been expanded from T_eff ∈ [3600, 6750] K to T_eff ∈ [3100, 14 500] K for the bright stars (G_RVS ≤ 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⁻¹ at G_RVS = 12 and 6.4 km s⁻¹ at G_RVS = 14 mag. The velocity zeropoint exhibits a small systematic trend with magnitude that starts around G_RVS = 11 mag and reaches about 400 m s⁻¹ at G_RVS = 14 mag. A correction formula is provided that can be applied to the published data. The Gaia DR3 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.