Gaia Data Release 2

Mapping the Milky Way disc kinematics

¹ GEPI, Observatoire de Paris, Université PSL, CNRS, 5 Place Jules Janssen, 92190 Meudon, France
² Science Support Office, Directorate of Science, European Space Research and Technology Centre (ESA/ESTEC), Keplerlaan 1, 2201AZ Noordwijk, The Netherlands
³ Institut de Ciències del Cosmos, Universitat de Barcelona (IEEC-UB), Martí i Franquès 1, 08028 Barcelona, Spain
⁴ INAF - Osservatorio Astrofisico di Torino, Via Osservatorio 20, 10025 Pino Torinese (TO), Italy
⁵ Institut UTINAM UMR6213, CNRS, OSU THETA Franche-Comté Bourgogne, Université Bourgogne Franche-Comté, 25000 Besançon, France
⁶ Mullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking, Surrey RH5 6NT, UK
⁷ Laboratoire d’Astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, Allée Geoffroy Saint-Hilaire, 33615 Pessac, France
⁸ Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
⁹ Università di Torino, Dipartimento di Fisica, Via Pietro Giuria 1, 10125 Torino, Italy
¹⁰ Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
¹¹ Leiden Observatory, Leiden University, Niels Bohrweg 2, 2333 CA Leiden, TheNetherlands
¹² INAF - Osservatorio Astronomico di Padova, Vicolo Osservatorio 5, 35122 Padova, Italy
¹³ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
¹⁴ Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstr. 12-14, 69120 Heidelberg, Germany
¹⁵ Department of Astronomy, University of Geneva, Chemin des Maillettes 51, 1290 Versoix, Switzerland
¹⁶ Mission Operations Division, Operations Department, Directorate of Science, European Space Research and Technology Centre (ESA/ESTEC), Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands
¹⁷ Lohrmann Observatory, Technische Universität Dresden, Mommsenstraße 13, 01062 Dresden, Germany
¹⁸ European Space Astronomy Centre (ESA/ESAC), Camino bajo del Castillo s/n, Urbanizacion Villafranca del Castillo, Villanueva de la Cañada, 28692 Madrid, Spain
¹⁹ Lund Observatory, Department of Astronomy and Theoretical Physics, Lund University, Box 43, 22100 Lund, Sweden
²⁰ Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, Bd de l’Observatoire, CS 34229, 06304 Nice Cedex 4, France
²¹ CNES Centre Spatial de Toulouse, 18 Av. Edouard Belin, 31401 Toulouse Cedex 9, France
²² Institut d’Astronomie et d’Astrophysique, Université Libre de Bruxelles CP 226, Bd du Triomphe, 1050 Brussels, Belgium
²³ F.R.S.-FNRS, Rue d’Egmont 5, 1000 Brussels, Belgium
²⁴ INAF - Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, 50125 Firenze, Italy
²⁵ Telespazio Vega UK Ltd for ESA/ESAC, Camino bajo del Castillo s/n, Urbanizacion Villafranca del Castillo, Villanueva de la Cañada, 28692 Madrid, Spain
²⁶ INAF - Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy
²⁷ Serco Gestión de Negocios for ESA/ESAC, Camino bajo del Castillo s/n, Urbanizacion Villafranca del Castillo, Villanueva de la Cañada, 28692 Madrid, Spain
²⁸ ALTEC S.p.a, Corso Marche 79, 10146 Torino, Italy
²⁹ Department of Astronomy, University of Geneva, Chemin d’Ecogia 16, 1290 Versoix, Switzerland
³⁰ Gaia DPAC Project Office, ESAC, Camino bajo del Castillo s/n, Urbanizacion Villafranca del Castillo, Villanueva de la Cañada, 28692 Madrid, Spain
³¹ SYRTE, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, LNE, 61 Av. de l’Observatoire, 75014 Paris, France
³² National Observatory of Athens, I. Metaxa and Vas. Pavlou, Palaia Penteli, 15236 Athens, Greece
³³ IMCCE, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Univ. Lille, 77 Av. Denfert-Rochereau, 75014 Paris, France
³⁴ Royal Observatory of Belgium, Ringlaan 3, 1180 Brussels, Belgium
³⁵ Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK
³⁶ Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
³⁷ Institut d’Astrophysique et de Géophysique, Université de Liège, 19c Allée du 6 Août, 4000 Liège, Belgium
³⁸ ATG Europe for ESA/ESAC, Camino bajo del Castillo s/n, Urbanizacion Villafranca del Castillo, Villanueva de la Cañada, 28692 Madrid, Spain
³⁹ Área de Lenguajes y Sistemas Informáticos, Universidad Pablo de Olavide, Ctra. de Utrera km 1., 41013 Sevilla, Spain
⁴⁰ ETSE Telecomunicación, Universidade de Vigo, Campus Lagoas-Marcosende, 36310 Vigo, Galicia, Spain
⁴¹ Large Synoptic Survey Telescope, 950 N. Cherry Av., Tucson, AZ 85719, USA
⁴² Observatoire Astronomique de Strasbourg, Université de Strasbourg, CNRS, UMR 7550, 11 Rue de l’Université, 67000 Strasbourg, France
⁴³ Kavli Institute for Cosmology, University of Cambridge, Madingley Road, Cambride CB3 0HA, UK
⁴⁴ Aurora Technology for ESA/ESAC, Camino bajo del Castillo s/n, Urbanizacion Villafranca del Castillo, Villanueva de la Cañada, 28692 Madrid, Spain
⁴⁵ Laboratoire Univers et Particules de Montpellier, Université Montpellier, Place Eugène Bataillon, CC72, 34095 Montpellier Cedex 05, France
⁴⁶ Department of Physics and Astronomy, Division of Astronomy and Space Physics, Uppsala University, Box 516, 75120 Uppsala, Sweden
⁴⁷ CENTRA, Universidade de Lisboa, FCUL, Campo Grande, Edif. C8, 1749-016 Lisboa, Portugal
⁴⁸ Università di Catania, Dipartimento di Fisica e Astronomia, Sezione Astrofisica, Via S. Sofia 78, 95123 Catania, Italy
⁴⁹ INAF - Osservatorio Astrofisico di Catania, via S. Sofia 78, 95123 Catania, Italy
⁵⁰ University of Vienna, Department of Astrophysics, Türkenschanzstraße 17, A1180 Vienna, Austria
⁵¹ CITIC – Department of Computer Science, University of A Coruña, Campus de Elviña s/n, 15071 A Coruña, Spain
⁵² CITIC – Astronomy and Astrophysics, University of A Coruña, Campus de Elviña s/n, 15071 A Coruña, Spain
⁵³ INAF - Osservatorio Astronomico di Roma, Via di Frascati 33, 00078 Monte Porzio Catone, 00040 Roma, Italy
⁵⁴ Space Science Data Center - ASI, Via del Politecnico SNC, 00133 Roma, Italy
⁵⁵ University of Helsinki, Department of Physics, P.O. Box 64, 00014 Helsinki, Finland
⁵⁶ Finnish Geospatial Research Institute – FGI, Geodeetinrinne 2, 02430 Masala, Finland
⁵⁷ Isdefe for ESA/ESAC, Camino bajo del Castillo s/n, Urbanizacion Villafranca del Castillo, Villanueva de la Cañada, 28692 Madrid, Spain
⁵⁸ STFC, Rutherford Appleton Laboratory, Harwell, Didcot OX11 0QX, UK
⁵⁹ Departamento de Inteligencia Artificial, UNED, c/ Juan del Rosal 16, 28040 Madrid, Spain
⁶⁰ Elecnor Deimos Space for ESA/ESAC, Camino bajo del Castillo s/n, Urbanizacion Villafranca del Castillo, Villanueva de la Cañada, 28692 Madrid, Spain
⁶¹ Thales Services for CNES – Centre Spatial de Toulouse, 18 Av. Edouard Belin, 31401 Toulouse Cedex 9, France
⁶² Department of Astrophysics/IMAPP, Radboud University, P.O. Box 9010, 6500 GL Nijmegen, The Netherlands
⁶³ European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany
⁶⁴ ON/MCTI-BR, Rua Gal. José Cristino 77, Rio de Janeiro CEP 20921-400, RJ, Brazil
⁶⁵ OV/UFRJ-BR, Ladeira Pedro Antônio 43, Rio de Janeiro CEP 20080-090, RJ, Brazil
⁶⁶ Department of Terrestrial Magnetism, Carnegie Institution for Science, 5241 Broad Branch Road, NW Washington, DC 20015-1305, USA
⁶⁷ Departamento de Astrofísica, Centro de Astrobiología (CSIC-INTA), ESA-ESAC, Camino Bajo del Castillo s/n, Villanueva de la Cañada, 28692 Madrid, Spain
⁶⁸ Leicester Institute of Space and Earth Observation and Departmentof Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH, UK
⁶⁹ Departamento de Estadística, Universidad de Cádiz, Calle República Árabe Saharawi s/n, Puerto Real, 11510 Cádiz, Spain
⁷⁰ Astronomical Institute Bern University, Sidlerstrasse 5, 3012 Bern, Switzerland
⁷¹ EURIX S.r.l., Corso Vittorio Emanuele II 61, 10128 Torino, Italy
⁷² Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
⁷³ HE Space Operations BV for ESA/ESAC, Camino bajo del Castillo s/n, Urbanizacion Villafranca del Castillo, Villanueva de la Cañada, 28692 Madrid, Spain
⁷⁴ Kapteyn Astronomical Institute, University of Groningen, Landleven 12, 9747 AD Groningen, The Netherlands
⁷⁵ SISSA - Scuola Internazionale Superiore di Studi Avanzati, Via Bonomea 265, 34136 Trieste, Italy
⁷⁶ University of Turin, Department of Computer Sciences, Corso Svizzera 185, 10149 Torino, Italy
⁷⁷ SRON, Netherlands Institute for Space Research, Sorbonnelaan 2, 3584CA Utrecht, The Netherlands
⁷⁸ Departamento de Matemática Aplicada y Ciencias de la Computación, Univ. de Cantabria, ETS Ingenieros de Caminos, Canales y Puertos, Avda. de los Castros s/n, 39005 Santander, Spain
⁷⁹ Unidad de Astronomía, Universidad de Antofagasta, Avenida Angamos 601, Antofagasta 1270300, Chile
⁸⁰ CRAAG - Centre de Recherche en Astronomie, Astrophysique et Géophysique, Route de l’Observatoire, BP 63 Bouzareah, 16340 Alger, Algeria
⁸¹ University of Antwerp, Onderzoeksgroep Toegepaste Wiskunde, Middelheimlaan 1, 2020 Antwerp, Belgium
⁸² INAF - Osservatorio Astronomico d’Abruzzo, Via Mentore Maggini, 64100 Teramo, Italy
⁸³ Instituto de Astronomia, Geofìsica e Ciências Atmosféricas, Universidade de São Paulo, Rua do Matão, 1226, Cidade Universitaria, 05508-900 São Paulo, SP, Brazil
⁸⁴ Department of Astrophysics, Astronomy and Mechanics, National and Kapodistrian University of Athens, Panepistimiopolis, Zografos, 15783 Athens, Greece
⁸⁵ Leibniz Institute for Astrophysics Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany
⁸⁶ RHEA for ESA/ESAC, Camino bajo del Castillo s/n, Urbanizacion Villafranca del Castillo, Villanueva de la Cañada, 28692 Madrid, Spain
⁸⁷ ATOS for CNES Centre Spatial de Toulouse, 18 Av. Edouard Belin, 31401 Toulouse Cedex 9, France
⁸⁸ School of Physics and Astronomy, Tel Aviv University, Tel Aviv 6997801, Israel
⁸⁹ UNINOVA - CTS, Campus FCT-UNL, Monte da Caparica, 2829-516 Caparica, Portugal
⁹⁰ School of Physics, O’Brien Centre for Science North, University College Dublin, Belfield, Dublin 4, Ireland
⁹¹ Dipartimento di Fisica e Astronomia, Università di Bologna, Via Piero Gobetti 93/2, 40129 Bologna, Italy
⁹² Barcelona Supercomputing Center - Centro Nacional de Supercomputación, c/ Jordi Girona 29, Ed. Nexus II, 08034 Barcelona, Spain
⁹³ Department of Computer Science, Electrical and Space Engineering, Luleå University of Technology, Box 848, 981 28 Kiruna, Sweden
⁹⁴ Max-Planck-Institut für Extraterrestrische Physik, High Energy Group, Gießenbachstraße, 85741 Garching, Germany
⁹⁵ Astronomical Observatory Institute, Faculty of Physics, Adam Mickiewicz University, Słoneczna 36, 60-286 Poznań, Poland
⁹⁶ Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences, Konkoly Thege Miklós út 15-17, 1121 Budapest, Hungary
⁹⁷ Eötvös Loránd University, Egyetem tér 1-3, 1053 Budapest, Hungary
⁹⁸ American Community Schools of Athens, 129 Aghias Paraskevis Ave. & Kazantzaki Street, Halandri, 15234 Athens, Greece
⁹⁹ Faculty of Mathematics and Physics, University of Ljubljana, Jadranska ulica 19, 1000 Ljubljana, Slovenia
¹⁰⁰ Villanova University, Department of Astrophysics and Planetary Science, 800 E Lancaster Av., Villanova PA 19085, USA
¹⁰¹ Physics Department, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium
¹⁰² McWilliams Center for Cosmology, Department of Physics, Carnegie Mellon University, 5000 Forbes Av., Pittsburgh, PA 15213, USA
¹⁰³ Astronomical Institute, Academy of Sciences of the Czech Republic, Fričova 298, 25165 Ondřejov, Czech Republic
¹⁰⁴ Telespazio for CNES Centre Spatial de Toulouse, 18 Av. Edouard Belin, 31401 Toulouse Cedex 9, France
¹⁰⁵ Institut de Physique de Rennes, Université de Rennes 1, 35042 Rennes, France
¹⁰⁶ INAF - Osservatorio Astronomico di Capodimonte, Via Moiariello 16, 80131 Napoli, Italy
¹⁰⁷ Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Rd, 200030 Shanghai, China
¹⁰⁸ School of Astronomy and Space Science, University of Chinese Academy of Sciences, Beijing 100049, China
¹⁰⁹ Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen Ø, Denmark
¹¹⁰ DXC Technology, Retortvej 8, 2500 Valby, Denmark
¹¹¹ Las Cumbres Observatory, 6740 Cortona Drive Suite 102, Goleta, CA 93117, USA
¹¹² Astrophysics Research Institute, Liverpool John Moores University, 146 Brownlow Hill, Liverpool L3 5RF, UK
¹¹³ Baja Observatory of University of Szeged, Szegedi út III/70, 6500 Baja, Hungary
¹¹⁴ Laboratoire AIM, IRFU/Service d’Astrophysique - CEA/DSM - CNRS - Université Paris Diderot, Bât 709, CEA-Saclay, 91191 Gif-sur-Yvette Cedex, France
¹¹⁵ Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa, Poland
¹¹⁶ Institute of Theoretical Physics, Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic
¹¹⁷ AKKA for CNES Centre Spatial de Toulouse, 18 Av. Edouard Belin, 31401 Toulouse Cedex 9, France
¹¹⁸ Vitrociset Belgium for ESA/ESAC, Camino bajo del Castillo s/n, Urbanizacion Villafranca del Castillo, Villanueva de la Cañada, 28692 Madrid, Spain
¹¹⁹ HE Space Operations BV for ESA/ESTEC, Keplerlaan 1, 2201AZ Noordwijk, The Netherlands
¹²⁰ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
¹²¹ QUASAR Science Resources for ESA/ESAC, Camino bajo del Castillo s/n, Urbanizacion Villafranca del Castillo, Villanueva de la Cañada, 28692 Madrid, Spain
¹²² Fork Research, Rua do Cruzado Osberno, Lt. 1, 9 esq., Lisboa, Portugal
¹²³ APAVE SUDEUROPE SAS for CNES Centre Spatial de Toulouse, 18 Av. Edouard Belin, 31401 Toulouse Cedex 9, France
¹²⁴ Nordic Optical Telescope, Rambla José Ana Fernández Pérez 7, 38711 Breña Baja, Spain
¹²⁵ Spanish Virtual Observatory, Spain
¹²⁶ Fundación Galileo Galilei - INAF, Rambla José Ana Fernández Pérez 7, 38712 Breña Baja, Santa Cruz de Tenerife, Spain
¹²⁷ INSA for ESA/ESAC, Camino bajo del Castillo s/n, Urbanizacion Villafranca del Castillo, Villanueva de la Cañada, 28692 Madrid, Spain
¹²⁸ Departamento Arquitectura de Computadores y Automática, Facultad de Informática, Universidad Complutense de Madrid, c/ Prof. José García Santesmases s/n, 28040 Madrid, Spain
¹²⁹ H H Wills Physics Laboratory, University of Bristol, Tyndall Av., Bristol BS8 1TL, UK
¹³⁰ Institut d’Estudis Espacials de Catalunya (IEEC), Gran Capita 2-4, 08034 Barcelona, Spain
¹³¹ Applied Physics Department, Universidade de Vigo, 36310 Vigo, Spain
¹³² Stellar Astrophysics Centre, Aarhus University, Department of Physics and Astronomy, 120 Ny Munkegade, Building 1520, 8000 Aarhus C, Denmark
¹³³ Argelander-Institut für Astronomie, Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany
¹³⁴ Research School of Astronomy and Astrophysics, Australian National University, Canberra 2611, ACT, Australia
¹³⁵ Sorbonne Universités, UPMC Univ. Paris 6 et CNRS, UMR 7095, Institut d’Astrophysique de Paris, 98 bis Bd. Arago, 75014 Paris, France
¹³⁶ Department of Geosciences, Tel Aviv University, Tel Aviv 6997801, Israel

Received: 20 February 2018
Accepted: 15 April 2018

Abstract

Context. The second Gaia data release (Gaia DR2) contains high-precision positions, parallaxes, and proper motions for 1.3 billion sources as well as line-of-sight velocities for 7.2 million stars brighter than G_RVS = 12 mag. Both samples provide a full sky coverage.

Aims. To illustrate the potential of Gaia DR2, we provide a first look at the kinematics of the Milky Way disc, within a radius of several kiloparsecs around the Sun.

Methods. We benefit for the first time from a sample of 6.4 million F-G-K stars with full 6D phase-space coordinates, precise parallaxes (σ_ϖ∕ϖ ≤ 20%), and precise Galactic cylindrical velocities (median uncertainties of 0.9-1.4 km s^-1 and 20% of the stars with uncertainties smaller than 1 km s^-1 on all three components). From this sample, we extracted a sub-sample of 3.2 million giant stars to map the velocity field of the Galactic disc from ~5 kpc to ~13 kpc from the Galactic centre and up to 2 kpc above and below the plane. We also study the distribution of 0.3 million solar neighbourhood stars (r < 200 pc), with median velocity uncertainties of 0.4 km s^-1, in velocity space and use the full sample to examine how the over-densities evolve in more distant regions. Results. Gaia DR2 allows us to draw 3D maps of the Galactocentric median velocities and velocity dispersions with unprecedented accuracy, precision, and spatial resolution. The maps show the complexity and richness of the velocity field of the galactic disc. We observe streaming motions in all the components of the velocities as well as patterns in the velocity dispersions. For example, we confirm the previously reported negative and positive galactocentric radial velocity gradients in the inner and outer disc, respectively. Here, we see them as part of a non-axisymmetric kinematic oscillation, and we map its azimuthal and vertical behaviour. We also witness a new global arrangement of stars in the velocity plane of the solar neighbourhood and in distant regions in which stars are organised in thin substructures with the shape of circular arches that are oriented approximately along the horizontal direction in the U − V plane. Moreover, in distant regions, we see variations in the velocity substructures more clearly than ever before, in particular, variations in the velocity of the Hercules stream. Conclusions. Gaia DR2 provides the largest existing full 6D phase-space coordinates catalogue. It also vastly increases the number of available distances and transverse velocities with respect to Gaia DR1. Gaia DR2 offers a great wealth of information on the Milky Way and reveals clear non-axisymmetric kinematic signatures within the Galactic disc, for instance. It is now up to the astronomical community to explore its full potential.