The structure and kinematics of the Milky Way disk in a view of a semi-analytic chemo-dynamic model

In this work we study the spatial structure as well as the chemical and kinematic properties of the Milky Way disk on the basis of a semi-analytic chemo-dynamical model from Just and Jahreiß (2010) (JJ model). Assuming inside-out formation and a constant thickness of the MW disk, we generalise the local JJ model to Galactocentric distances of R = 4-12 kpc. At each radius we assume a star formation rate (SFR) with a peak shifting to younger ages for the outer disk and use the four-slope broken power-law initial mass function (IMF) from Rybizki and Just (2015). The age-velocity dispersion and age-metallicity relations (AVR and AMR) are then obtained self-consistently; the latter is constrained by metallicity distributions of the Red Clump stars from the Apache Point Observatory Galactic Evolution Experiment (APOGEE, Eisenstein et al., 2011). Within a forward modelling framework, we validate the local JJ model in the solar cylinder by testing it against the samples from the Radial Velocity Experiment (RAVE, Steinmetz et al., 2006) and the first and second Gaia data releases (DR1 and DR2, Lindegren et al., 2016; Gaia Collaboration et al., 2018). We find an overall mismatch in star counts up to ~9%, with a statistically significant discrepancy identified for the dynamically cold populations. We also develop a new treatment of the asymmetric drift and apply it in three metallicity bins to the RAVE local sample and G-dwarfs from the Sloan Extension for Galactic Understanding and Exploration (SEGUE, Yanny et al., 2009). The tangential component of the solar peculiar motion obtained from the RAVE sample is V = 4.47 ± 0.8 km/s. The rotation curve reconstructed from the SEGUE G-dwarfs in a range of distances R = 7-10 kpc has a near-zero slope of 0.033 ± 0.034. The thick disk G-dwarfs are found to be kinematically homogeneous with a scale length of 2.05 ± 0.22 kpc, which is in agreement with values from the literature

Collinder 135 and UBC 7: A Physical Pair of Open Clusters

Given the closeness of the two open clusters Cr 135 and UBC 7 on the sky, we investigate the possibility of the two clusters to be physically related. We aim to recover the present-day stellar membership in the open clusters Collinder 135 and UBC 7 (300 pc from the Sun), to constrain their kinematic parameters, ages and masses, and to restore their primordial phase space configuration. The most reliable cluster members are selected with our traditional method modified for the use of Gaia DR2 data. Numerical simulations use the integration of cluster trajectories backwards in time with our original high order Hermite4 code \PGRAPE. We constrain the age, spatial coordinates and velocities, radii and masses of the clusters. We estimate the actual separation of the cluster centres equal to 24 pc. The orbital integration shows that the clusters were much closer in the past if their current line-of-sight velocities are very similar and the total mass is more than 7 times larger the mass of the determined most reliable members. We conclude that the two clusters Cr 135 and UBC 7 might very well have formed a physial pair, based on the observational evidence as well as numerical simulations. The probability of a chance coincidence is only about $2\%$.Comment: Accepted for publication as a Letter in Astronomy and Astrophysics. 5 pages, 2 figure

The sixth data release of the Radial Velocity Experiment (RAVE). I. Survey description, spectra and radial velocities

The Radial Velocity Experiment (RAVE) is a magnitude-limited (9<I<12) spectroscopic survey of Galactic stars randomly selected in the southern hemisphere. The RAVE medium-resolution spectra (R~7500) cover the Ca-triplet region (8410-8795A). The 6th and final data release (DR6 or FDR) is based on 518387 observations of 451783 unique stars. RAVE observations were taken between 12 April 2003 and 4 April 2013. Here we present the genesis, setup and data reduction of RAVE as well as wavelength-calibrated and flux-normalized spectra and error spectra for all observations in RAVE DR6. Furthermore, we present derived spectral classification and radial velocities for the RAVE targets, complemented by cross matches with Gaia DR2 and other relevant catalogs. A comparison between internal error estimates, variances derived from stars with more than one observing epoch and a comparison with radial velocities of Gaia DR2 reveals consistently that 68% of the objects have a velocity accuracy better than 1.4 km/s, while 95% of the objects have radial velocities better than 4.0 km/s. Stellar atmospheric parameters, abundances and distances are presented in subsequent publication. The data can be accessed via the RAVE Web (http://rave-survey.org) or the Vizier database.Comment: 32 pages, 11 figures, accepted for publication to A

The Sixth Data Release of the Radial Velocity Experiment (R ave). II. Stellar Atmospheric Parameters, Chemical Abundances, and Distances

We present part 2 of the sixth and final Data Release (DR6) of the Radial Velocity Experiment (Rave), a magnitude-limited spectroscopic survey of Galactic stars randomly selected in Earth's southern hemisphere. The Rave medium-resolution spectra (R ∼ 7500) cover the Ca triplet region (8410-8795 Å) and span the complete time frame from the start of Rave observations on 2003 April 12 to their completion on 2013 April 4. In the second of two publications, we present the data products derived from 518,387 observations of 451,783 unique stars using a suite of advanced reduction pipelines focusing on stellar atmospheric parameters, in particular purely spectroscopically derived stellar atmospheric parameters, and the overall metallicity), enhanced stellar atmospheric parameters inferred via a Bayesian pipeline using Gaia DR2 astrometric priors, and asteroseismically calibrated stellar atmospheric parameters for giant stars based on asteroseismic observations for 699 K2 stars. In addition, we provide abundances of the elements Fe, Al, and Ni, as well as an overall [α/Fe] ratio obtained using a new pipeline based on the GAUGUIN optimization method that is able to deal with variable signal-to-noise ratios. The Rave DR6 catalogs are cross-matched with relevant astrometric and photometric catalogs, and are complemented by orbital parameters and effective temperatures based on the infrared flux method. The data can be accessed via the Rave website (http://rave-survey.org) or the Vizier database.Funding for Rave has been provided by: the Leibniz-Institut f¨ur Astrophysik Potsdam (AIP); the Australian Astronomical Observatory; the Australian National University; the Australian Research Council; the French National Research Agency (Programme National Cosmology et Galaxies (PNCG) of CNRS/INSU with INP and IN2P3, co-funded by CEA and CNES); the German Research Foundation (SPP 1177 and SFB 881); the European Research Council (ERC-StG 240271 Galactica); the Istituto Nazionale di Astrofisica at Padova; The Johns Hopkins University; the National Science Foundation of the USA (AST-0908326); the W. M. Keck foundation; the Macquarie University; the Netherlands Research School for Astronomy; the Natural Sciences and Engineering Research Council of Canada; the Slovenian Research Agency (research core funding no. P1-0188); the Swiss National Science Foundation; the Science & Technology Facilities Council of the UK; Opticon; Strasbourg Observatory; and the Universities of Basel, Groningen, Heidelberg, and Sydney. PJM is supported by grant 2017-03721 from the Swedish Research Council. LC is the recipient of the ARC Future Fellowship FT160100402. RAG acknowledges the support from the PLATO CNES grant. SM would like to acknowledge support from the Spanish Ministry with the Ramon y Cajal fellowship number RYC-2015-17697. MS thanks the Research School of Astronomy & Astrophysics in Canberra for support through a Distinguished Visitor Fellowship. RFGW thanks the Kavli Institute for Theoretical Physics and the Simons Foundation for support as a Simons Distinguished Visiting Scholar. This research was supported in part by the National Science Foundation under Grant No. NSF PHY-1748958 to KITP

The Sixth Data Release of the Radial Velocity Experiment (R AVE). I. Survey Description, Spectra, and Radial Velocities

The Radial Velocity Experiment (Rave) is a magnitude-limited (9 < I < 12) spectroscopic survey of Galactic stars randomly selected in Earth's southern hemisphere. The Rave medium-resolution spectra (R ∼ 7500) cover the Ca-triplet region (8410-8795 Å). The sixth and final data release (DR6) is based on 518,387 observations of 451,783 unique stars. Rave observations were taken between 2003 April 12 and 2013 April 4. Here we present the genesis, setup, and data reduction of Rave as well as wavelength-calibrated and flux-normalized spectra and error spectra for all observations in Rave DR6. Furthermore, we present derived spectral classification and radial velocities for the Rave targets, complemented by cross-matches with Gaia DR2 and other relevant catalogs. A comparison between internal error estimates, variances derived from stars with more than one observing epoch, and a comparison with radial velocities of Gaia DR2 reveals consistently that 68% of the objects have a velocity accuracy better than 1.4 km s-1, while 95% of the objects have radial velocities better than 4.0 km s-1. Stellar atmospheric parameters, abundances and distances are presented in a subsequent publication. The data can be accessed via the Rave website (http://rave-survey.org) or the Vizier database.Funding for Rave has been provided by: the Leibniz-Institut f¨ur Astrophysik Potsdam (AIP); the Australian Astronomical Observatory; the Australian National University; the Australian Research Council; the French National Research Agency (Programme National Cosmology et Galaxies (PNCG) of CNRS/INSU with INP and IN2P3, co-funded by CEA and CNES); the German Research Foundation (SPP 1177 and SFB 881); the European Research Council (ERC-StG 240271 Galactica); the Istituto Nazionale di Astrofisica at Padova; The Johns Hopkins University; the National Science Foundation of the USA (AST-0908326); the W. M. Keck foundation; the Macquarie University; the Netherlands Research School for Astronomy; the Natural Sciences and Engineering Research Council of Canada; the Slovenian Research Agency (research core funding no. P1-0188); the Swiss National Science Foundation; the Science & Technology Facilities Council of the UK; Opticon; Strasbourg Observatory; and the Universities of Basel, Groningen, Heidelberg, and Sydney. PJM is supported by grant 2017-03721 from the Swedish Research Council. LC is the recipient of the ARC Future Fellowship FT160100402. RAG acknowledges the support from the PLATO CNES grant. SM would like to acknowledge support from the Spanish Ministry with the Ramon y Cajal fellowship number RYC-2015-17697. MS thanks the Research School of Astronomy & Astrophysics in Canberra for support through a Distinguished Visitor Fellowship. RFGW thanks the Kavli Institute for Theoretical Physics and the Simons Foundation for support as a Simons Distinguished Visiting Scholar. This research was supported in part by the National Science Foundation under Grant No. NSF PHY-1748958 to KITP

The Sixth Data Release of the Radial Velocity Experiment (RAVE). II. Stellar Atmospheric Parameters, Chemical Abundances, and Distances

We present part 2 of the sixth and final Data Release (DR6) of the Radial Velocity Experiment (RAVE), a magnitude-limited (9 < I < 12) spectroscopic survey of Galactic stars randomly selected in Earth's southern hemisphere. The RAVE medium-resolution spectra (R ∼ 7500) cover the Ca triplet region (8410-8795 Å) and span the complete time frame from the start of RAVE observations on 2003 April 12 to their completion on 2013 April 4. In the second of two publications, we present the data products derived from 518,387 observations of 451,783 unique stars using a suite of advanced reduction pipelines focusing on stellar atmospheric parameters, in particular purely spectroscopically derived stellar atmospheric parameters (Teff, log g, and the overall metallicity), enhanced stellar atmospheric parameters inferred via a Bayesian pipeline using Gaia DR2 astrometric priors, and asteroseismically calibrated stellar atmospheric parameters for giant stars based on asteroseismic observations for 699 K2 stars. In addition, we provide abundances of the elements Fe, Al, and Ni, as well as an overall [α/Fe] ratio obtained using a new pipeline based on the GAUGUIN optimization method that is able to deal with variable signal-to-noise ratios. The RAVE DR6 catalogs are cross-matched with relevant astrometric and photometric catalogs, and are complemented by orbital parameters and effective temperatures based on the infrared flux method. The data can be accessed via the RAVE website (http://rave-survey.org) or the Vizier database

The Sixth Data Release of the Radial Velocity Experiment (RAVE). I. Survey Description, Spectra, and Radial Velocities

The Radial Velocity Experiment (Rave) is a magnitude-limited (9 < I < 12) spectroscopic survey of Galactic stars randomly selected in Earth's southern hemisphere. The Rave medium-resolution spectra (R ∼ 7500) cover the Ca-triplet region (8410-8795 Å). The sixth and final data release (DR6) is based on 518,387 observations of 451,783 unique stars. Rave observations were taken between 2003 April 12 and 2013 April 4. Here we present the genesis, setup, and data reduction of Rave as well as wavelength-calibrated and flux-normalized spectra and error spectra for all observations in Rave DR6. Furthermore, we present derived spectral classification and radial velocities for the Rave targets, complemented by cross-matches with Gaia DR2 and other relevant catalogs. A comparison between internal error estimates, variances derived from stars with more than one observing epoch, and a comparison with radial velocities of Gaia DR2 reveals consistently that 68% of the objects have a velocity accuracy better than 1.4 km s-1, while 95% of the objects have radial velocities better than 4.0 km s-1. Stellar atmospheric parameters, abundances and distances are presented in a subsequent publication. The data can be accessed via the Rave website (http://rave-survey.org) or the Vizier database