3D kinematics and age distribution of the Open Cluster population
Y. Tarricq, C. Soubiran, L. Casamiquela, T. Cantat-Gaudin, L. Chemin, F. Anders, T. Antoja, M. Romero-Gómez, F. Figueras, C. Jordi, A. Bragaglia, L. Balaguer-Nú… 展开作者
Y. Tarricq, C. Soubiran, L. Casamiquela, T. Cantat-Gaudin, L. Chemin, F. Anders, T. Antoja, M. Romero-Gómez, F. Figueras, C. Jordi, A. Bragaglia, L. Balaguer-Núñez, R. Carrera, A. Castro-Ginard, A. Moitinho, P. Ramos, D. Bossini
备注：
Accepted for publication in A&A, 16 pages, 14 figures
Open Clusters (OCs) can trace with a great accuracy the evolution of the Galactic disk. The aim of this work is to study the kinematical behavior of the OC population over time. We take advantage of the latest age determinations of OCs to investigate the correlations of the 6D phase space coordinates and orbital properties with age. We also investigate the rotation curve of the Milky Way traced by OCs and we compare it to that of other observational or theoretical studies. We gathered nearly 30000 Radial Velocity (RV) measurements of OC members from both Gaia-RVS data and ground based surveys and catalogues. We computed the weighted mean RV, Galactic velocities and orbital parameters of 1382 OCs. We investigated their distributions as a function of age, and by comparison to field stars. We provide the largest RV catalogue available for OCs, half of it based on at least 3 members. Compared to field stars, we note that OCs are not exactly on the same arches in the radial-azimuthal velocity plane, while they seem to follow the same diagonal ridges in the Galactic radial distribution of azimuthal velocities. Velocity ellipsoids in different age bins all show a clear anisotropy. The heating rate of the OC population is similar to that of field stars for the radial and azimuthal components but significantly lower for the vertical component. The rotation curve drawn by our sample of clusters shows several dips, which match the wiggles derived from non-axisymmetric models of the Galaxy. From the computation of orbits, we obtain a clear dependence of the maximum height and eccentricity with age. Finally, the orbital characteristics of the sample of clusters as shown by the action variables, follow the distribution of field stars. The additional age information of the clusters points towards some (weak) age dependence of the known moving groups.
The internal dynamics of multiple stellar populations in Globular Clusters (GCs) provides unique constraints on the physical processes responsible for their formation. Specifically, the present-day kinematics of cluster stars, such as rotation and velocity dispersion, seems to be related to the initial configuration of the system. In recent work (Milone et al. 2018), we analyzed for the first time the kinematics of the different stellar populations in NGC0104 (47Tucanae) over a large field of view, exploiting the Gaia Data Release 2 proper motions combined with multi-band ground-based photomet…
In the last three decades several hundred nearby members of young stellar moving groups (MGs) have been identified, but there has been less systematic effort to quantify or characterise young stars that do not belong to previously identified MGs. Using a kinematically unbiased sample of 225 lithium-rich stars within 100 pc, we find that only $50 \pm 10$ per cent of young ($\lesssim 125$ Myr), low-mass ($0.5<M/M_{\odot}<1.0$) stars, are kinematically associated with known MGs. Whilst we find some evidence that six of the non-MG stars may be connected with the Lower Centaurus-Crux association, t…
Recent results using radial-velocity measurements from the Gaia-ESO Survey have led to the discovery of multiple kinematic populations across the Vela OB2 association. We present here a proper-motion study of the same region. Our aim is to test whether the radial-velocity populations have a counterpart in proper-motion space, and if so, how the two sets of kinematical data complement each other. This work is based on parallaxes and proper motions from the TGAS catalog, as part of Gaia DR1. Two distinct proper-motion populations are found dispersed across ~5 degrees (or ~30 pc at their likely d…
We combine MUSE spectroscopy and Hubble Space Telescope ultraviolet (UV) photometry to perform a study of the chemistry and dynamics of the Galactic globular cluster Messier 80 (M80, NGC 6093). Previous studies have revealed three stellar populations that not only vary in their light-element abundances, but also in their radial distributions, with concentration decreasing with increasing nitrogen enrichment. This remarkable trend, which sets M80 apart from the other Galactic globular clusters, points towards a complex formation and evolutionary history. To better understand how M80 formed and …
Numerous observational studies have revealed the ubiquitous presence of multiple stellar populations in globular clusters and cast many hard challenges for the study of the formation and dynamical history of these stellar systems. In this Letter we present the results of a study of the kinematic properties of multiple populations in NGC 2808 based on high-precision Hubble Space Telescope proper-motion measurements. In a recent study, Milone et al. have identified five distinct populations (A, B, C, D, and E) in NGC 2808. Populations D and E coincide with the helium-enhanced populations in the …
The internal dynamics of multiple stellar populations in Globular Clusters (GCs) provides unique constraints on the physical processes responsible for their formation. Specifically, the present-day kinematics of cluster stars, such as rotation and velocity-dispersion, could be related to the initial configuration of the system. In recent work, we provided the first study of the kinematics of different stellar populations in NGC$\,$0104 over a large field of view in the plane of the sky, exploiting Gaia Data Release 2 (DR2) proper motions combined with multi-band ground-based photometry. In thi…
Using the newly commissioned KCWI instrument on the Keck-II telescope, we analyse the stellar kinematics and stellar populations of the well-studied massive early-type galaxy (ETG) NGC 1407. We obtained high signal-to-noise integral-field-spectra for a central and an outer (around one effective radius towards the south-east direction) pointing with integration times of just 600s and 2400s, respectively. We confirm the presence of a kinematically distinct core also revealed by VLT/MUSE data of the central regions. While NGC 1407 was previously found to have stellar populations characteristic of…
Several scenarios have been proposed to explain the presence of multiple stellar populations in globular clusters. Many of them invoke multiple generations of stars to explain the observed chemical abundance anomalies, but it has also been suggested that self-enrichment could occur via accretion of ejecta from massive stars onto the circumstellar disc of low-mass pre-main sequence stars. These scenarios imply different initial conditions for the kinematics of the various stellar populations. Given some net angular momentum initially, models for which a second generation forms from gas that col…
Gaia DR2 provides an unprecedented sample of stars with full 6D phase-space measurements, creating the need for a self-consistent means of discovering and characterising the phase-space overdensities known as moving groups or associations. Here we present Chronostar, a new Bayesian analysis tool that meets this need. Chronostar uses the Expectation-Maximisation algorithm to remove the circular dependency between association membership lists and fits to their phase-space distributions, making it possible to discover unknown associations within a kinematic data set. It uses forward-modelling of …
Our understanding of the kinematic properties of multiple stellar populations (mPOPs) in Galactic globular clusters (GCs) is still limited compared to what we know about their chemical and photometric characteristics. Such limitation arises from the lack of a comprehensive observational investigation of this topic. Here we present the first homogeneous kinematic analysis of mPOPs in 56 GCs based on high-precision proper motions computed with Hubble Space Telescope data. We focused on red-giant-branch stars, for which the mPOP tagging is clearer, and measured the velocity dispersion of stars be…
We present a method to build a probability density function (pdf) for the age of a star based on its peculiar velocities $U$, $V$ and $W$ and its orbital eccentricity. The sample used in this work comes from the Geneva-Copenhagen Survey (GCS) which contains both the spatial velocities, orbital eccentricities and isochronal ages for about $14\,000$ stars. Using the GCS stars, we fitted the parameters that describe the relations between the distributions of kinematical properties and age. This parametrization allows us to obtain an age probability from the kinematical data. From this age pdf, we…
Post-starburst galaxies host a population of early-type stars (A or F), but simultaneously lack indicators of ongoing star formation such as OII emission. Two distinct stellar populations have been identified in these systems: a young post-starburst population superimposed on an older host population. We present a study of nine post-starburst galaxies with the following objectives: 1) to investigate if and how kinematical differences between the young and old populations of stars can be measured; and 2) to gain insight into the formation mechanism of the young population in these systems. We f…
Empirical and theoretical studies have demonstrated that the periods of Mira variable stars are related to their ages. This, together with their brightness in the infrared, makes them powerful probes of the formation and evolution of highly-extincted or distant parts of the Local Group. Here we utilise the Gaia DR3 catalogue of long-period variable candidates to calibrate the period-age relation of the Mira variables. Dynamical models are fitted to the O-rich Mira variable population across the extended solar neighbourhood and then the resulting solar neighbourhood period-kinematic relations a…
The formation process of multiple populations in globular clusters is still up for debate. Kinematic differences between the populations are particularly interesting in this respect, because they allow us to distinguish between single-epoch formation scenarios and multi-epoch formation scenarios. We analyze the kinematics of 25 globular clusters and aim to find kinematic differences between multiple populations to constrain their formation process. We split red-giant branch (RGB) stars in each cluster into three populations (P1, P2, P3) for the type-II clusters and two populations (P1 and P2) …
We present the results of a suite of \Nbody simulations aimed at understanding the fundamental aspects of the long-term evolution of the internal kinematics of multiple stellar populations in globular clusters. Our models enable us to study the cooperative effects of internal, relaxation-driven processes and external, tidally-induced perturbations on the structural and kinematic properties of multiple-population globular clusters. To analyse the dynamical behaviour of the multiple stellar populations in a variety of spin-orbit coupling conditions, we have considered three reference cases in wh…
We present a study of the three dimensional structure, kinematics, and age distribution of the Orion OB association, based on the second data release of the Gaia satellite (Gaia DR2). Our goal is to obtain a complete picture of the star formation history of the Orion complex and to relate our findings to theories of sequential and triggered star formation. We select the Orion population with simple photometric criteria, and we construct a three dimensional map in galactic Cartesian coordinates to study the physical arrangement of the stellar clusters in the Orion region. The map shows structur…
A joint JWST and HST view of Omega Centauri: Multiple stellar populations and their kinematics
Univ. di Padova（帕多瓦大学）；Istituto Nazionale di Astrofisica - Osservatorio Astronomico di Padova（意大利国家天体物理研究所-帕多瓦天文台）；Research School of Astronomy & Astrophysics, Australian National University（澳大利亚国立大学天文与天体物理研究学院）
The nearest region of massive star formation - the Scorpius-Centaurus OB2 association (Sco-Cen) - is a local laboratory ideally suited to the study of a wide range of astrophysical phenomena. Precision astrometry from the Gaia mission has expanded the census of this region by an order of magnitude. However, Sco-Cen's vastness and complex substructure make kinematic analysis of its traditional three regions, Upper Scorpius, Upper Centaurus-Lupus and Lower Centaurus-Crux, challenging. Here we use Chronostar, a Bayesian tool for kinematic age determination, to carry out a new kinematic decomposit…
We present the analysis of the radial distributions and kinematic properties of the multiple stellar populations (mPOPs) hosted in the globular cluster (GC) NGC 6352 as part of the Hubble Space Telescope (HST) "UV Legacy Survey of Galactic Globular Clusters" program. NGC 6352 is one of the few GCs for which the mPOP tagging in appropriate color-magnitude diagrams is clear in all evolutionary sequences. We computed high-precision stellar proper motions for the stars from the cluster's core out to 75 arcsec ($\sim$1.5 core radii, or $\sim$0.6 half-light radii). We find that, in the region explor…
The kinematics and dynamics of young stellar populations enable us to test theories of star formation. With this aim, we continue our analysis of the SDSS-III/APOGEE IN-SYNC survey, a high resolution near infrared spectroscopic survey of young clusters. We focus on the Orion A star-forming region, for which IN-SYNC obtained spectra of $\sim2700$ stars. In Paper IV we used these data to study the young stellar population. Here we study the kinematic properties through radial velocities ($v_r$). The young stellar population remains kinematically associated with the molecular gas, following a $\s…
The series of events, which occurred at high redshift and originated multiple stellar populations in Globular Clusters (GCs) are still poorly understood. Theoretical work suggests that the present-day dynamics of stars in nearby GCs, including the rotation and velocity dispersion, may retain important clues on the formation of multiple populations. So far, the dynamics of multiple populations have been investigated either from radial velocities of a relatively-small sample of stars, or from relative proper motions of stars in the small field of view provided by the Hubble Space Telescope. In t…
Stellar associations can be discerned as overdensities of sources not only in the physical space but also in the velocity space. The common motion of their members, gradually eroded by the galactic tidal field, is partially reminiscent of the initial kinematic structure. Using recent data from Gaia EDR3, combined with radial velocities from GALAH and APOGEE, we traced back the present positions of stars belonging to Upper Scorpius, a subgroup of Scorpius-Centaurus, the nearest OB association. About one half of the subgroup (the "clustered" population) appears composed of many smaller entities,…
We present a new theoretical population synthesis model (the Galaxy Model) to examine and deal with large amounts of data from surveys of the Milky Way and to decipher the present and past structure and history of our own Galaxy. We assume the Galaxy to consist of a superposition of many composite stellar populations belonging to the thin and thick disks, the stellar halo and the bulge, and to be surrounded by a single dark matter halo component. A global model for the Milky Way's gravitational potential is built up self-consistently with the density profiles from the Poisson equation. In turn…
Stellar kinematics provides the key to understanding the formation process and dynamical evolution of stellar systems. Here, we present a kinematic study of the massive star-forming region W4 in the Cassiopeia OB6 association using the Gaia Data Release 2 and high-resolution optical spectra. This star-forming region is composed of a core cluster (IC 1805) and a stellar population distributed over 20 pc, which is a typical structural feature found in many OB associations. According to a classical model, this structural feature can be understood in the context of the dynamical evolution of a sta…
The Vela-Puppis region is known to host the Vela OB2 association as well as several young clusters featuring OB and pre-main sequence stars. Several spatial and kinematic subgroups have been identified in the recent years. By grouping stars based on their positions and velocity we can address the quetion of the dynamical history of the region and the mechanisms that drove stellar formation. The Gaia DR2 astrometry and photometry enables us to characterise the 3D spatial and 3D kinematic distribution of young stars and to estimate the ages of the identified components. We use an unsupervised cl…
We find two chemically distinct populations separated relatively cleanly in the [Fe/H] - [Mg/Fe] plane, but also distinguished in other chemical planes, among metal-poor stars (primarily with metallicities [Fe/H] $< -0.9$) observed by the Apache Point Observatory Galactic Evolution Experiment (APOGEE) and analyzed for Data Release 13 (DR13) of the Sloan Digital Sky Survey. These two stellar populations show the most significant differences in their [X/Fe] ratios for the $α$-elements, C+N, Al, and Ni. In addition to these populations having differing chemistry, the low metallicity high-Mg popul…
We discuss constraints on the formation of multiple populations in globular clusters (GCs) imposed by their present-day kinematics (velocity dispersion and anisotropy) and spatial distribution. We argue that the observational evidence collected so far in the outer parts of clusters is generally consistent with an enriched population forming more centrally concentrated compared to the primordial population, in agreement with all the scenarios proposed to date (in some cases by design), but not sufficient to favour a particular scenario. We highlight that the differential rotation of subpopulati…
Sco OB2 is the nearest OB association, extending over approximately 2000 sq.deg. on the sky. Only its brightest members are already known (from Hipparcos) across its entire size, while studies of its lower-mass population refer only to small portions of its extent. In this work we exploit the capabilities of Gaia DR2 measurements to search for Sco OB2 members across its entire size and down to the lowest stellar masses. We use both Gaia astrometric and photometric data to select association members, using minimal assumptions derived mostly from the Hipparcos studies. Gaia resolves small detail…
We present a spectral decomposition technique that separates the contribution of different kinematic components in galaxies from the observed spectrum. This allows to study the kinematics and properties of the stellar populations of the individual components (e.g., bulge, disk, counter-rotating cores, orthogonal structures). Here, we discuss the results of this technique for galaxies that host counter-rotating stellar disks of comparable size. In all the studied cases, the counter-rotating stellar disk is the less massive, the youngest and has different chemical content (metallicity and alpha-…
In the $Gaia$ era stellar kinematics are extensively used to study Galactic halo stellar populations, to search for halo structures, and to characterize the interface between the halo and hot disc populations. We use distribution function-based models of modern datasets with 6D phase space data to qualitatively describe a variety of kinematic spaces commonly used in the study of the Galactic halo. Furthermore, we quantitatively assess how well each kinematic space can separate radially anisotropic from isotropic halo populations. We find that scaled action space (the ``action diamond'') is sup…
The variations of kinematic parameters with age are considered for a sample of 15 402 thin-disk O--F stars with accurate $α$, $δ$, $μ$, and $π>3$ mas from the Hipparcos catalogue and radial velocities from the PCRV catalogue. The ages have been calculated from the positions of the stars on the Hertzsprung--Russell diagram relative to the isochrones from the Padova database by taking into account the extinction from the previously constructed 3D analytical model and extinction coefficient $R_V$ from the 3D map of its variations. Smooth, mutually reconciled variations of the velocity dispersions…
We report results of proper motions of 15 known Large Magellanic Cloud (LMC) old globular clusters (GCs) derived from the Gaia DR2 data sets. When these mean proper motions are gathered with existent radial velocity measurements to compose the GCs' velocity vectors, we found that the projection of the velocity vectors onto the LMC plane and those perpendicular to it tell us about two distinct kinematic GC populations. Such a distinction becomes clear if the GCs are split at a perpendicular velocity of 10 km/s (absolute value). The two different kinematic groups also exhibit different spatial d…
We present a detailed comparison of the Milky Way (MW) globular cluster (GC) kinematics with the 25 Milky Way-mass cosmological simulations from the E-MOSAICS project. While the MW falls within the kinematic distribution of GCs spanned by the simulations, the relative kinematics of its metal-rich ($[\rm{Fe/H}]>-1.2$) versus metal-poor ($[\rm{Fe/H}]<-1.2$), and inner ($r<8\rm{kpc}$) versus outer ($r>8\rm{kpc}$) populations are atypical for its mass. To understand the origins of these features, we perform a comprehensive statistical analysis of the simulations, and find 18 correlations describin…
The kinematics and dynamics of stellar and substellar populations within young, still-forming clusters provides valuable information for constraining theories of formation mechanisms. Using Keck II NIRSPEC+AO data, we have measured radial velocities for 56 low-mass sources within 4' of the core of the Orion Nebula Cluster (ONC). We also re-measure radial velocities for 172 sources observed with SDSS/APOGEE. These data are combined with proper motions measured using $HST$ ACS/WFPC2/WFC3IR and Keck II NIRC2, creating a sample of 135 sources with all three velocity components. The velocities meas…
Studying the stellar kinematics of galaxies is a key tool in the reconstruction of their evolution. However, the current measurements of the stellar kinematics are complicated by several factors, including dust extinction and the presence of multiple stellar populations. We use integral field spectroscopic data of four galaxies from the TIMER survey to explore and compare the kinematics measured in different spectral regions that are sensitive to distinct stellar populations. We derive the line-of-sight velocity and velocity dispersion of both a young (<2 Gyr) and an old stellar population fro…
The origin of multiple stellar populations in Globular Clusters (GCs) is one of the greatest mysteries of modern stellar astrophysics. N-body simulations suggest that the present-day dynamics of GC stars can constrain the events that occurred at high redshift and led to the formation of multiple populations. Here, we combine multi-band photometry from the Hubble Space Telescope (HST) and ground-based facilities with HST and Gaia Data Release 2 proper motions to investigate the spatial distributions and the motions in the plane of the sky of multiple populations in the type II GCs NGC 5139 ($ω\…
We present an analysis of Galactic bulge stars from Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) observations of the Stanek window (l,b=[0.25,-2.15]) from two epochs approximately two years apart. This dataset is adjacent to the provisional Wide-field Infrared Survey Telescope (WFIRST) microlensing field. Proper motions are measured for approximately 115,000 stars down to 28th mag in V band and 25th mag in I band, with accuracies of 0.5 mas yr$^{-1}$ (20 km s$^{-1}$) at I $\approx$ 21. A cut on the longitudinal proper motion $μ_l$ allows us to separate disk and bulge populations and…
We consider interesting results on the kinematics of the bulge, beginning with Mould's (1983) measurement of the velocity dispersion of the late M giants in the bulge, and carrying the discussion on to the present day, to discuss the largest survey ever undertaken of luminous SiO maser AGB stars. This SiO maser population of AGB stars is too luminous to have evolved from the oldest globular cluster age stellar population, yet has a velocity dispersion consistent with the oldest populations (the red clump stars) in the bulge. We identify two groups of maser stars by their kinematics; the subgro…
We combine photometric metallicities with astrometry from Gaia DR3 to examine the chemodynamic structure of ~250,000 K dwarfs in the Solar Neighborhood (SN). In kinematics, we observe ridges/clumps of "kinematic groups", like studies of more massive main-sequence stars. Here we note clear differences in both metallicity and vertical velocity as compared to the surrounding regions in velocity space and hypothesize this is due to differences in mean age. To test this, we develop a method to estimate the age distribution of sub-populations of stars. In this method, we use GALAH data to define pro…
We derive the mean velocity components at various Galactocentric radii from 8 to 14 kpc using about 40,000 red clump stars observed in the LAMOST survey. We find that the vertical bulk motion for younger red clump stars are significantly larger than that for the older red clump stars. This is likely the kinematical feature of the Galactic warp around its line-of-node, which is located close to the Galactic anti-center region. It is evident that the warp are mainly contributed by the younger stars rather than the older stars. The age variation in the vertical kinematics favors a formation scena…
Over 4,000 exoplanets have been identified and thousands of candidates are to be confirmed. The relations between the characteristics of these planetary systems and the kinematics, Galactic components, and ages of their host stars have yet to be well explored. Aiming to addressing these questions, we conduct a research project, dubbed as PAST (Planets Across Space and Time). To do this, one of the key steps is to accurately characterize the planet host stars. In this paper, the Paper I of the PAST series, we revisit the kinematic method for classification of Galactic components and extend the …
Context. Many disk galaxies host two extended stellar components that rotate in opposite directions. The analysis of the stellar populations of the counter-rotating components provides constraints on the environmental and internal processes that drive their formation. Aims. The S0 NGC 1366 in the Fornax cluster is known to host a stellar component that is kinematically decoupled from the main body of the galaxy. Here we successfully separated the two counter-rotating stellar components to independently measure the kinematics and properties of their stellar populations. Methods. We performed a …
In this paper, we consider the problem of reconstructing a galaxy's stellar population-kinematic distribution function from optical integral field unit measurements. These quantities are connected via a high-dimensional integral equation. To solve this problem, we propose a projected Nesterov-Kaczmarz reconstruction (PNKR) method, which efficiently leverages the problem structure and incorporates physical prior information such as smoothness and non-negativity constraints. To test the performance of our reconstruction approach, we apply it to a dataset simulated from a known ground truth densi…
We present a detailed analysis of the kinematic properties of the multiple populations (MPs) in the low-mass Galactic globular cluster NGC6362 based on a sample of about 500 member stars for which radial velocities (RVs), Fe and Na abundances have been homogeneously derived. At distances from the cluster center larger than about 0.5 $r_h$, we find that first (FG - Na-poor) and second generation (SG - Na-rich) stars show hints of different line-of-sight velocity dispersion profiles, with FG stars being dynamically hotter. This is the first time that differences in the velocity dispersion of MPs…
We present Gemini GMOS-IFU data of eight compact low-mass early-type galaxies (ETGs) in the Virgo cluster. We analyse their stellar kinematics, stellar population, and present two-dimensional maps of these properties covering the central 5"x 7" region. We find a large variety of kinematics: from non- to highly-rotating objects, often associated with underlying disky isophotes revealed by deep images from the Next Generation Virgo Cluster Survey. In half of our objects, we find a centrally-concentrated younger and more metal-rich stellar population. We analyze the specific stellar angular momen…
We present the integral-field kinematics and stellar population properties of 64 galaxies (61 are Early-Type galaxies, ETGs) with Counter-Rotating stellar Disks (CRD) selected from about 4000 galaxies in the MaNGA survey, based on evidence of counter-rotation or two velocity dispersion peaks in the kinematic maps. For 17 CRDs, the counter-rotating components can also be separated spectroscopically. The frequency of CRDs in MaNGA is <5% for ellipticals, <3% for lenticulars and <1% for spirals (at 95% confidence level), consistent with previous estimates. We produced age and metallicity maps, an…
