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The nearest stars provide a fundamental constraint for our understanding of stellar physics and the Galaxy. The nearby sample serves as an anchor where all objects can be seen and understood with precise data. This work is triggered by the most recent data release of the astrometric space mission Gaia and uses its unprecedented high precision parallax measurements to review the census of objects within 10 pc. The first aim of this work was to compile all stars and brown dwarfs within 10 pc observable by Gaia, and compare it with the Gaia Catalogue of Nearby Stars as a quality assurance test. We complement the list to get a full 10 pc census, including bright stars, brown dwarfs, and exoplanets. We started our compilation from a query on all objects with a parallax larger than 100 mas using SIMBAD. We completed the census by adding companions, brown dwarfs with recent parallax measurements not in SIMBAD yet, and vetted exoplanets. The compilation combines astrometry and photometry from the recent Gaia Early Data Release 3 with literature magnitudes, spectral types and line-of-sight velocities. We give a description of the astrophysical content of the 10 pc sample. We find a multiplicity frequency of around 28%. Among the stars and brown dwarfs, we estimate that around 61% are M stars and more than half of the M stars are within the range M3.0 V to M5.0 V. We give an overview of the brown dwarfs and exoplanets that should be detected in the next Gaia data releases along with future developments. We provide a catalogue of 540 stars, brown dwarfs, and exoplanets in 339 systems, within 10 pc from the Sun. This list is as volume-complete as possible from current knowledge and provides benchmark stars that can be used, for instance, to define calibration samples and to test the quality of the forthcoming Gaia releases. It also has a strong outreach potential., Comment: Revised version. Accepted for publication in A&A. 15 pages, 3 figures. The catalogue will be only available in electronic form at https://gruze.org/10pc/, at https://gucds.inaf.it/, and at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/

Context. Extratidal stars are stellar bodies that end up outside the tidal radius of a cluster as a result of internal processes or external forces acting upon it. The presence and spatial distribution of these stars can give us insights into the past evolution of a cluster inside our Galaxy. Aims. Previous works suggest that globular clusters, when explored in detail, show evidence of extratidal stars. We aim to search for possible extratidal stars in the Galactic globular clusters NGC 6397, NGC 2808, and NGC 6266 using the photometry and proper motion measurements from Gaia DR2 database (Gaia Collaboration et al. 2018). Results. Finally, 120, 126, and 107 extratidal candidate stars were found lying outside the tidal radius of the globular clusters NGC 6397, NGC 2808, and NGC 6266, respectively. 70%, 25.4%, and 72.9% of the extratidal stars found are located outside the Jacobi radius of NGC 6397, NGC 2808, and NGC 6266, respectively. The spatial distribution of the extratidal stars belonging to NGC 6397 appears S-like, extending along the curved leading and trailing arms. NGC 2808 has an overdensity of stars in the trailing part of the cluster and NGC 6266 seems to have overdensities of extratidal stars in its eastern and northern sides. Conclusions. Proper motions and color-magnitude diagrams can be used to identify extratidal candidate stars around GCs. Nonetheless, depending on how different the kinematics and stellar populations of a cluster are compared to the Milky Way field, the fraction of contamination can be larger. All three clusters are found to have extratidal stars outside their tidal radii. For NGC 6397 and NGC 2808, these stars may be the result of a combined effect of the disc shocks and tidal disruptions. For NGC 6266, the distribution of extratidal stars is symmetrical around it, most likely indicating that the cluster has an extended stellar envelope., Comment: Accepted for publication in Astronomy and Astrophysics

The cornerstone mission of the European Space Agency, Gaia, has revealed properties of 260 000 white dwarfs in the Galaxy, allowing us for the first time to constrain the evolution of white dwarfs with a large sample. Complementary surveys (CoRoT,Kepler, K2, APOGEE andGaia-ESO), will revolutionize our understanding of the formation and history of our Galaxy, providing accurate stellar masses, radii, ages, distances, and chemical properties for very large samples of stars across different Galactic stellar populations. To exploit the potential of the combination of spectroscopic, seismic and astrometric observations, the population synthesis approach is a very crucial and efficient tool. We develop the Besan\c{c}on Galaxy model (BGM, Lagarde et al.2017) for which stellar evolution predictions are included, providing the global asteroseismic properties and the surface chemical abundances along the evolution of low- and intermediate-mass stars. For the first time, the BGM can explore the effects of an extra-mixing occurring in red-giant stars (Lagarde et al.2019), changing their stellar properties. The nextstep is to model a consistent treatment of giant stars and their remnants (e.g., white dwarfs).This kind of improvement would help us to constrain stellar and Galactic evolutions.

We present an analysis of the structure, kinematics and orbit of a newly found stellar stream emanating from the globular cluster M92 (NGC 6341). This stream was discovered in an improved matched-filter map of the outer Galaxy, based on a "color-color-magnitude" diagram, created using photometry from the Canada-France Imaging Survey (CFIS) and the Pan-STARRS 1 3$\pi$ survey (PS1). We find the stream to have a length of 17{\deg} (2.5 kpc at the distance of M92), a width dispersion of $0.29${\deg}(42 pc) and a stellar mass of $[3.17 \pm{0.89}] \times 10^{4} $ M$_\odot$ ($10 \%$ of the stellar mass of the current main body of M92). We examine the kinematics of main sequence, red giant and blue horizontal branch stars belonging to the stream and that have proper motion measurements from the second data release of Gaia. N-body simulations suggest that the stream was likely formed very recently (during the last $\sim 500$ Myr) forcing us to question the orbital origin of this ancient, metal-poor globular cluster., Comment: 14 pages, 8 figures. Accepted for publication in ApJ

We analyse the kinematics and dynamics of a homogeneous sample of red clump stars selected from the second Gaia data release catalogue in the direction of the Galactic poles. The level of completeness of the sample at heights between 0.6 and 3.5 kpc is asserted by comparison with the 2 Micron All Sky Survey catalogue. We show that both the density distribution and velocity dispersion are significantly more perturbed in the North than in the South, in all analysed regions of our Galactic neighbourhoods. We provide a detailed assessment of these North-South asymmetries at large heights. We then proceed to evaluate how such asymmetries could affect determinations of the dynamical matter density under equilibrium assumptions. We find that a Jeans analysis delivers relatively similar vertical forces and integrated dynamical surface densities at large heights above the plane in both hemispheres. At these heights, the densities of stars and gas are very low and the surface density is largely dominated by dark matter, which allows to estimate, separately in the North and South, the local dark matter density derived under equilibrium assumptions. In the presence of vertical perturbations, such values should be considered as an upper limit. This Jeans analysis yields values of the local dark matter density above 2~kpc, $\rho_{\rm DM} \sim 0.013 \, {\rm M}_\odot/{\rm pc}^3$ ($ \sim 0.509 \, {\rm GeV/cm}^3$) in the perturbed Northern hemisphere, and $\rho_{\rm DM} \sim 0.010 \, {\rm M}_\odot/{\rm pc}^3$ ($ \sim 0.374 \, {\rm GeV/cm}^3$) in the much less perturbed South. As a comparison, we determine the local dark matter density by fitting a global phase-space distribution to the data. We end up with a value in the range of $\rho_{\rm DM} \sim 0.011 - 0.014 \, {\rm M}_\odot/{\rm pc}^3$ in global agreement with Jeans analysis., Comment: 16 pages, 14 figures, accepted in A&A

We propose a new mission called Space Project for Astrophysical and Cosmological Exploration (SPACE) as part on the ESA long term planning Voyage 2050 programme. SPACE will study galaxy evolution at the earliest times, with the key goals of charting the formation of the heavy elements, measuring the evolution of the galaxy luminosity function, tracing the build-up of stellar mass in galaxies over cosmic time, and finding the first super-massive black holes (SMBHs) to form. The mission will exploit a unique region of the parameter space, between the narrow ultra-deep surveys with HST and JWST, and shallow wide-field surveys such as Roman Space Telescope and EUCLID, and should yield by far the largest sample of any current or planned mission of very high redshift galaxies at z > 10 which are sufficiently bright for detailed follow-up spectroscopy. Crucially, we propose a wide-field spectroscopic near-IR + mid-IR capability which will greatly enhance our understanding of the first galaxies by detecting and identifying a statistical sample of the first galaxies and the first SMBH, and to chart the metal enrichment history of galaxies in the early Universe - potentially finding signatures of the very first stars to form from metal-free primordial gas. The wide-field and wavelength range of SPACE will also provide us a unique opportunity to study star formation by performing a wide survey of the Milky Way in the near-IR + mid-IR. This science project can be enabled either by a stand-alone ESA-led M mission or by an instrument for an L mission (with ESA and/or NASA, JAXA and other international space agencies) with a wide-field (sub-)millimetre capability at wavelength > 500 microns., Comment: Submitted to Experimental Astronomy as one of the proposals for the European Space Agency Voyage 2050 Programme

We present a new fully data-driven algorithm that uses photometric data from the Canada-France-Imaging-Survey (CFIS; $u$), Pan-STARRS 1 (PS1; $griz$), and Gaia ($G$) to discriminate between dwarf and giant stars and to estimate their distances and metallicities. The algorithm is trained and tested using the SDSS/SEGUE spectroscopic dataset and Gaia photometric/astrometric dataset. At [Fe/H]$<-1.2$, the algorithm succeeds in identifying more than 70% of the giants in the training/test set, with a dwarf contamination fraction below 30% (with respect to the SDSS/SEGUE dataset). The photometric metallicity estimates have uncertainties better than 0.2 dex when compared with the spectroscopic measurements. The distances estimated by the algorithm are valid out to a distance of at least $\sim 80$ kpc without requiring any prior on the stellar distribution, and have fully independent uncertainities that take into account both random and systematic errors. These advances allow us to estimate these stellar parameters for approximately 12 million stars in the photometric dataset. This will enable studies involving the chemical mapping of the distant outer disc and the stellar halo, including their kinematics using the Gaia proper motions. This type of algorithm can be applied in the Southern hemisphere to the first release of LSST data, thus providing an almost complete view of the external components of our Galaxy out to at least $\sim 80$ kpc. Critical to the success of these efforts will be ensuring well-defined spectroscopic training sets that sample a broad range of stellar parameters with minimal biases. A catalogue containing the training/test set and all relevant parameters within the public footprint of CFIS is available online., Comment: 27 pages. 21 Figures. Accepted for publication in AAS. Training/testing sample available at: http://www.canfar.net/storage/list/gthomas/dwarfOrGiants.fits

We report the identification of possible extended star debris candidates beyond the cluster tidal radius of NGC 6362 based on the second {\it Gaia} data release ({\it Gaia} DR2). We found 259 objects possibly associated with the cluster lying in the vicinity of the giant branch and 1--2 magnitudes fainter/brighter than the main-sequence turn-off in the cluster color-magnitude diagram and which cover an area on the sky of $\sim$4.1 deg$^{2}$ centered on the cluster. We traced back the orbit of NGC 6362 in a realistic Milky-Way potential, using the \texttt{GravPot16} package, for 3 Gyrs. The orbit shows that the cluster shares similar orbital properties as the inner disk, having peri-/apo-galactic distances, and maximum vertical excursion from the Galactic plane inside the corotation radius (CR), moving inwards from CR radius to visit the inner regions of the Milky Way. The dynamical history of the cluster reveals that it has crossed the Galactic disk several times in its lifetime and has recently undergone a gravitational shock, $\sim 15.9$ Myr ago, suggesting that less than 0.1\% of its mass has been lost during the current disk-shocking event. Based on the cluster's orbit and position in the Galaxy, we conclude that the possible extended star debris candidates are a combined effect of the shocks from the Galactic disk and evaporation from the cluster. Lastly, the evolution of the vertical component of the angular momentum shows that the cluster is strongly affected dynamically by the Galactic bar potential., Comment: 10 pages, 4 figures, 3 tables. Accepted to the Monthly Notices of the Royal Astronomical Society

We report the discovery of a unique collection of metal-poor giant-stars, that exhibit anomalously high levels of $^{28}$Si, clearly above typical Galactic levels. Our sample spans a narrow range of metallicities, peaking at $-1.07\pm 0.06$, and exhibit abundance ratios of [Si,Al/Fe] that are as extreme as those observed in Galactic globular clusters (GCs), and Mg is slightly less overabundant. In almost all the sources we used, the elemental abundances were re-determined from high-resolution spectra, which were re-analyzed assuming LTE. Thus, we compiled the main element families, namely the light elements (C, N), $\alpha-$elements (O, Mg, Si), iron-peak element (Fe), $\textit{s}-$process elements (Ce, Nd), and the light odd-Z element (Al). We also provide dynamical evidence that most of these stars lie on tight (inner)halo-like and retrograde orbits passing through the bulge. Such kinds of objects have been found in present-day halo GCs, providing the clearest chemical signature of past accretion events in the (inner) stellar halo of the Galaxy, formed possibly as the result of dissolved halo GCs. Their chemical composition is, in general, similar to that of typical GCs population, although several differences exist., Comment: 11 pages, 5 figures, 2 table; accepted for publication in ApJ Letters

We report the serendipitous discovery of a nitrogen-rich, mildly metal-poor ([Fe/H]=-1.08) giant star in a single-lined spectroscopic binary system found in the SDSS-IV Apache Point Observatory Galactic Evolution Experiment (APOGEE-2) survey, Data Release 14 (DR14). Previous work has assumed that the two percent of halo giants with unusual elemental abundances have been evaporated from globular clusters, but other origins for their abundance signatures, including binary mass transfer, must also be explored. We present the results of an abundance re-analysis of the APOGEE-2 high-resolution near-infrared spectrum of 2M12451043+1217401 with the Brussels Automatic Stellar Parameter (BACCHUS) automated spectral analysis code, and re-derive manually the main element families, namely the light elements (C, N), elements (O, Mg, Si), iron-peak element (Fe), \textit{s}-process element (Ce), and the light odd-Z element (Al). Our analysis confirm the N-rich nature of 2M12451043+1217401, which has a [N/Fe] ratio of $+0.69$, and shows that the abundances of C and Al are slightly discrepant from that of a typical mildly metal-poor RGB star, but exhibit Mg, Si, O and \textit{s}-process abundances (Ce) of typical field stars. We also detect a particularly large variability in its radial velocity over the period of the APOGEE-2 observations, and the most likely orbit fit to the radial velocity data has a period of $730.89\pm106.86$ days, a velocity semi-amplitude of $9.92 \pm 0.14$ km s$^{-1}$, and an eccentricity of $\sim 0.1276 \pm0.1174$, which support the hypothesis of a binary companion, and that has probably been polluted by a now-extinct AGB star., Comment: Accepted for publication in A&A, 13 pages, 8 figures, 7 tables

We present the chemical distribution of the Milky Way, based on 2,900$\, {\rm deg^2}$ of $u$-band photometry taken as part of the Canada-France Imaging Survey. When complete, this survey will cover 10,000$\, {\rm deg^2}$ of the Northern sky. By combing the CFHT $u$-band photometry together with SDSS and Pan-STARRS $g,r,$ and $i$, we demonstrate that we are able to measure reliably the metallicities of individual stars to $\sim 0.2$ dex, and hence additionally obtain good photometric distance estimates. This survey thus permits the measurement of metallicities and distances of the dominant main-sequence population out to approximately 30 kpc, and provides much higher number of stars at large extraplanar distances than have been available from previous surveys. We develop a non-parametric distance-metallicity decomposition algorithm and apply it to the sky at $30\deg < |b| < 70\deg$ and to the North Galactic Cap. We find that the metallicity-distance distribution is well-represented by three populations whose metallicity distributions do not vary significantly with vertical height above the disk. As traced in main-sequence stars, the stellar halo component shows a vertical density profile that is close to exponential, with a scale height of around 3 kpc. This may indicate that the inner halo was formed partly from disk stars ejected in an ancient minor merger., Comment: 21 pages, 17 figures, accepted for publication in ApJ

The Canada-France Imaging Survey (CFIS) will map the northern high Galactic latitude sky in the $u$-band ("CFIS-u", 10,000$\, {\rm deg^2}$) and in the $r$-band ("CFIS-r", 5,000$\, {\rm deg^2}$), enabling a host of stand-alone science investigations, and providing some of the ground-based data necessary for photometric redshift determination for the Euclid mission. In this first contribution we present the $u$-band component of the survey, describe the observational strategy, and discuss some first highlight results, based on approximately one third of the final area. We show that the Galactic anticenter structure is distributed continuously along the line of sight, out to beyond 20 kpc, and possesses a metallicity distribution that is essentially identical to that of the outer disk sampled by APOGEE. This suggests that it is probably a buckled disk of old metal-rich stars, rather than a stream or a flare. We also discuss the future potential for CFIS-u in discovering star-forming dwarf galaxies around the Local Group, the characterization of the white dwarf and blue straggler population of the Milky Way, as well as its sensitivity to low-surface brightness structures in external galaxies., Comment: 12 pages, 11 figures, accepted for publication in ApJ

We attempt to constrain the kinematics of the thin and thick disks using the Besancon population synthesis model together with RAVE DR4 and Gaia first data release (TGAS). The RAVE fields were simulated by applying a detailed target selection function and the kinematics was computed using velocity ellipsoids depending on age in order to study the secular evolution. We accounted for the asymmetric drift computed from fitting a Stackel potential to orbits. Model parameters such as velocity dispersions, mean motions, and velocity gradients were adjusted using an ABC-MCMC method. We made use of the metallicity to enhance the separation between thin and thick disks. We show that this model is able to reproduce the kinematics of the local disks in great detail. The disk follows the expected secular evolution, in very good agreement with previous studies of the thin disk. The new asymmetric drift formula, fitted to our previously described St\"ackel potential, fairly well reproduces the velocity distribution in a wide solar neighborhood. The U and W components of the solar motion determined with this method agree well with previous studies. However, we find a smaller V component than previously thought, essentially because we include the variation of the asymmetric drift with distance to the plane. The thick disk is represented by a long period of formation (at least 2 Gyr), during which, as we show, the mean velocity increases with time while the scale height and scale length decrease, very consistently with a collapse phase with conservation of angular momentum. This new Galactic dynamical model is able to reproduce the observed velocities in a wide solar neighborhood at the quality level of the TGAS-RAVE sample, allowing us to constrain the thin and thick disk dynamical evolution, as well as determining the solar motion., Comment: Astronomy and Astrophysics in press, 18 pages, 10 figures, 1 appendix; revised with modified discussion and language editing

We re-analyse photometric near-infrared data in order to investigate why it is so hard to get a consensus for the shape and density law of the bulge, as seen from the literature. To solve the problem we use the Besancon Galaxy Model to provide a scheme for parameter fitting of the structural characteristics of the bulge region. The fitting process allows the determination of the global shape of the bulge main structure. We explore various parameters and shape for the bulge/bar structure based on Ferrer's ellipsoids and fit the shape of the inner disc in the same process. The results show that the main structure is a quite standard triaxial boxy bar/bulge with an orientation of about 13 degree with respect to the Sun-centre direction. But the fit is greatly improved when we add a second structure, which is a longer and thicker ellipsoid. We emphasize that our first ellipsoid represent the main boxy bar of the Galaxy, and that the thick bulge could be either a classical bulge slightly flattened by the effect of the bar potential, or a inner thick disc counterpart. We show that the double clump seen at intermediate latitudes can be reproduced by adding a slight flare to the bar. In order to better characterize the populations, we further simulate several fields which have been surveyed in spectroscopy and for which metallicity distribution function (MDF) are available. The model is in good agreement with these MDF along the minor axis if we assume that the main bar has a mean solar metallicity and the second thicker population has a lower metallicity. It then creates naturally a vertical metallicity gradient by the mixing of the two poulations. (abridged), Comment: 16 pages, 17 figures, Astronomy and Astrophysics in press, new submission after langage editing and minor corrections (including the title)