Gaia Data Release 2: The kinematics of globular clusters and dwarf galaxies around the Milky Way

Aims. The goal of this paper is to demonstrate the outstanding quality of the second data release of the Gaia mission and its power for constraining many different aspects of the dynamics of the satellites of the Milky Way. We focus here on determining the proper motions of 75 Galactic globular clusters, nine dwarf spheroidal galaxies, one ultra-faint system, and the Large and Small Magellanic Clouds.Methods. Using data extracted from the Gaia archive, we derived the proper motions and parallaxes for these systems, as well as their uncertainties. We demonstrate that the errors, statistical and systematic, are relatively well understood. We integrated the orbits of these objects in three different Galactic potentials, and characterised their properties. We present the derived proper motions, space velocities, and characteristic orbital parameters in various tables to facilitate their use by the astronomical community.Results. Our limited and straightforward analyses have allowed us for example to (i) determine absolute and very precise proper motions for globular clusters; (ii) detect clear rotation signatures in the proper motions of at least five globular clusters; (iii) show that the satellites of the Milky Way are all on high-inclination orbits, but that they do not share a single plane of motion; (iv) derive a lower limit for the mass of the Milky Way of 9.1-2.6+6.2 × 1011 M⊙ based on the assumption that the Leo I dwarf spheroidal is bound; (v) derive a rotation curve for the Large Magellanic Cloud based solely on proper motions that is competitive with line-of-sight velocity curves, now using many orders of magnitude more sources; and (vi) unveil the dynamical effect of the bar on the motions of stars in the Large Magellanic Cloud.Conclusions. All these results highlight the incredible power of the Gaia astrometric mission, and in particular of its second data release.</div

<i>Gaia</i> Data Release 3. Summary of the content and survey properties

Context.We present the third data release of the European Space Agency’sGaiamission,GaiaDR3. This release includes a large variety of new data products, notably a much expanded radial velocity survey and a very extensive astrophysical characterisation ofGaiasources.Aims.We outline the content and the properties ofGaiaDR3, providing an overview of the main improvements in the data processing in comparison with previous data releases (where applicable) and a brief discussion of the limitations of the data in this release.Methods.TheGaiaDR3 catalogue is the outcome of the processing of raw data collected with theGaiainstruments during the first 34 months of the mission by theGaiaData Processing and Analysis Consortium.Results.TheGaiaDR3 catalogue contains the same source list, celestial positions, proper motions, parallaxes, and broad band photometry in theG,GBP, andGRPpass-bands already present in the Early Third Data Release,GaiaEDR3.GaiaDR3 introduces an impressive wealth of new data products. More than 33 million objects in the rangesGRVS < 14 and 3100 < Teff < 14 500, have new determinations of their mean radial velocities based on data collected byGaia. We provideGRVSmagnitudes for most sources with radial velocities, and a line broadening parameter is listed for a subset of these. MeanGaiaspectra are made available to the community. TheGaiaDR3 catalogue includes about 1 million mean spectra from the radial velocity spectrometer, and about 220 million low-resolution blue and red prism photometer BP/RP mean spectra. The results of the analysis of epoch photometry are provided for some 10 million sources across 24 variability types.GaiaDR3 includes astrophysical parameters and source class probabilities for about 470 million and 1500 million sources, respectively, including stars, galaxies, and quasars. Orbital elements and trend parameters are provided for some 800 000 astrometric, spectroscopic and eclipsing binaries. More than 150 000 Solar System objects, including new discoveries, with preliminary orbital solutions and individual epoch observations are part of this release. Reflectance spectra derived from the epoch BP/RP spectral data are published for about 60 000 asteroids. Finally, an additional data set is provided, namely theGaiaAndromeda Photometric Survey, consisting of the photometric time series for all sources located in a 5.5 degree radius field centred on the Andromeda galaxy.Conclusions.This data release represents a major advance with respect toGaiaDR2 andGaiaEDR3 because of the unprecedented quantity, quality, and variety of source astrophysical data. To date this is the largest collection of all-sky spectrophotometry, radial velocities, variables, and astrophysical parameters derived from both low- and high-resolution spectra and includes a spectrophotometric and dynamical survey of SSOs of the highest accuracy. The non-single star content surpasses the existing data by orders of magnitude. The quasar host and galaxy light profile collection is the first such survey that is all sky and space based. The astrophysical information provided inGaiaDR3 will unleash the full potential ofGaia’s exquisite astrometric, photometric, and radial velocity surveys