- ID:
- ivo://CDS.VizieR/J/A+A/594/A120
- Title:
- Gaia-ESO Survey: Hydrogen lines in red giants
- Short Name:
- J/A+A/594/A120
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Red giant stars are perhaps the most important type of stars for Galactic and extra-galactic archaeology: they are luminous, occur in all stellar populations, and their surface temperatures allow precise abundance determinations for many different chemical elements. Yet, the full star formation and enrichment history of a galaxy can be traced directly only if two key observables can be determined for large stellar samples: age and chemical composition. While spectroscopy is a powerful method to analyse the detailed abundances of stars, stellar ages are the missing link in the chain, since they are not a direct observable. However, spectroscopy should be able to estimate stellar masses, which for red giants directly infer ages provided their chemical composition is known. Here we establish a new empirical relation between the shape of the hydrogen line in the observed spectra of red giants and stellar mass determined from asteroseismology. The relation allows determining stellar masses and ages with an accuracy of 10-15%. The method can be used with confidence for stars in the following range of stellar parameters: 4000<T_eff_<5000K, 0.5<logg<3.5, -2.0<[Fe/H]<0.3, and luminosities logL/L_{sun}_<2.5. Our analysis provides observational evidence that the H_{alpha}_ spectral characteristics of red giant stars are tightly correlated with their mass and therefore their age. We also show that the method samples well all stellar populations with ages above 1Gyr. Targeting bright giants, the method allows obtaining simultaneous age and chemical abundance information far deeper than would be possible with asteroseismology, extending the possible survey volume to remote regions of the Milky Way and even to neighbouring galaxies such as Andromeda or the Magellanic Clouds even with current instrumentation, such as the VLT and Keck facilities.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/574/L7
- Title:
- Gaia-ESO Survey: Li-rich stars in NGC2547
- Short Name:
- J/A+A/574/L7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The nearby (distance ~350-400pc), rich Vela OB2 association, includes gamma^2^ Velorum, one of the most massive binaries in the solar neighborhood, and is an excellent laboratory for investigating the formation and early evolution of young clusters. Recent Gaia-ESO survey observations led to the discovery of two kinematically distinct populations in the young (10-15Myr) cluster immediately surrounding gamma^2^ Velorum. Here we analyse the results of Gaia-ESO survey observations of NGC 2547, a 35Myr cluster located two degrees south of gamma^2^ Velorum. The radial velocity distribution of lithium-rich pre-main sequence stars shows a secondary population, kinematically distinct and younger than NGC 2547. The radial velocities, lithium absorption lines, and the positions in a color-magnitude diagram of this secondary population are consistent with those of one of the components discovered around gamma^2^ Velorum. This result shows that there is a young, low-mass stellar population spread over at least several square degrees in the Vela OB2 association. This population could have originally been part of a cluster around gamma^2^ Velorum that expanded after gas expulsion, or formed in a less dense environment spread over the whole Vela OB2 region.
1263. Gaia-ESO Survey: NGC6705
- ID:
- ivo://CDS.VizieR/J/A+A/569/A17
- Title:
- Gaia-ESO Survey: NGC6705
- Short Name:
- J/A+A/569/A17
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Chemically inhomogeneous populations are observed in most globular clusters, but not in open clusters. Cluster mass seems to play a key role in the existence of multiple populations. Studying the chemical homogeneity of the most massive open clusters is needed to better understand the mechanism of their formation and determine the mass limit under which clusters cannot host multiple populations. Here we studied NGC 6705, which is a young and massive open cluster located towards the inner region of the Milky Way. This cluster is located inside the solar circle. This makes it an important tracer of the inner disk abundance gradient. This study makes use of BVI and ri photometry and comparisons with theoretical isochrones to derive the age of NGC 6705. We study the density profile of the cluster and the mass function to infer the cluster mass. Based on abundances of the chemical elements distributed in the first internal data release of the Gaia-ESO Survey, we study elemental ratios and the chemical homogeneity of the red clump stars. Radial velocities enable us to study the rotation and internal kinematics of the cluster.
- ID:
- ivo://CDS.VizieR/J/MNRAS/505/1135
- Title:
- Gaia/IPHAS catalogue of Ha-excess sources
- Short Name:
- J/MNRAS/505/1135
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- We present a catalogue of point-like H{alpha}-excess sources in the Northern Galactic Plane. Our catalogue is created using a new technique that leverages astrometric and photometric information from Gaia to select H{alpha}-bright outliers in the INT Photometric H{alpha} Survey of the Northern Galactic Plane (IPHAS), across the colour-absolute magnitude diagram. To mitigate the selection biases due to stellar population mixing and to extinction, the investigated objects are first partitioned with respect to their positions in the Gaia colour-absolute magnitude space, and in the Galactic coordinates space, respectively. The selection is then performed on both partition types independently. Two significance parameters are assigned to each target, one for each partition type. These represent a quantitative degree of confidence that the given source is a reliable H{alpha}-excess candidate, with reference to the other objects in the corresponding partition. Our catalogue provides two flags for each source, both indicating the significance level of the H{alpha}-excess. By analysing their intensity in the H{alpha} narrow band, 28496 objects out of 7474835 are identified as H{alpha}-excess candidates with a significance higher than 3. The completeness fraction of the H{alpha} outliers selection is between 3% and 5%. The suggested 5sigma conservative cut yields a purity fraction of 81.9%.
- ID:
- ivo://CDS.VizieR/IV/36
- Title:
- Gaia-IPHAS/KIS Value-Added Catalogues
- Short Name:
- IV/36
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a sub-arcsecond cross-match of Gaia DR2 (Cat. I/345) against the INT Photometric H-alpha Survey of the Northern Galactic Plane Data Release 2 (IPHAS DR2, Cat. II/321) and the Kepler-INT Survey (KIS, Cat. J/AJ/144/24). The resulting value-added catalogues (VACs) provide additional precise photometry to the Gaia photometry (r, i and H-alpha for IPHAS, with additional U and g for KIS). In building the catalogue, proper motions given in Gaia DR2 are wound back to match the epochs of IPHAS DR2, thus ensuring high proper motion objects are appropriately cross-matched. The catalogues contain 7927224 and 791071 sources for IPHAS and KIS, respectively. The requirement of >5 sigma parallax detection for every included source means that distances out to 1-1.5kpc are well covered. We define two additional parameters for each catalogued object: (i) fc, a magnitude-dependent tracer of the quality of the Gaia astrometric fit; (ii) fFP, the false-positive rate for parallax measurements determined from astrometric fits of a given quality at a given magnitude. Selection cuts based on these parameters can be used to clean colour-magnitude and colour-colour diagrams in a controlled and justified manner. We provide both full and light versions of the VAC, with VAC-light containing only objects that represent our recommended trade-off between purity and completeness. Uses of the catalogues include the identification of new variable stars in the matched data sets, and more complete identification of H-alpha-excess emission objects thanks to separation of high-luminosity stars from the main sequence.
- ID:
- ivo://CDS.VizieR/J/AJ/160/108
- Title:
- Gaia-Kepler stellar properties catalog. II. Planets
- Short Name:
- J/AJ/160/108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Studies of exoplanet demographics require large samples and precise constraints on exoplanet host stars. Using the homogeneous Kepler stellar properties derived using the Gaia Data Release 2 by Berger et al., we recompute Kepler planet radii and incident fluxes and investigate their distributions with stellar mass and age. We measure the stellar mass dependence of the planet radius valley to be dlogR_p/d_logM_{star}_=0.26_-0.16_^+0.21^, consistent with the slope predicted by a planet mass dependence on stellar mass (0.24-0.35) and core-powered mass loss (0.33). We also find the first evidence of a stellar age dependence of the planet populations straddling the radius valley. Specifically, we determine that the fraction of super-Earths (1-1.8{R_{Earth}_) to sub-Neptunes (1.8-3.5R_{Earth}_) increases from 0.61{+/-}0.09 at young ages (<1Gyr) to 1.00{+/-}0.10 at old ages (>1Gyr), consistent with the prediction by core-powered mass loss that the mechanism shaping the radius valley operates over Gyr timescales. Additionally, we find a tentative decrease in the radii of relatively cool (Fp<150{F}_{Earth}_) sub-Neptunes over Gyr timescales, which suggests that these planets may possess H/He envelopes instead of higher mean molecular weight atmospheres. We confirm the existence of planets within the hot sub-Neptunian "desert" (2.2R_{Earth}_<Rp<3.8R_{Earth}_, Fp>650F_{Earth}_) and show that these planets are preferentially orbiting more evolved stars compared to other planets at similar incident fluxes. In addition, we identify candidates for cool (Fp<20F_{Earth}_) inflated Jupiters, present a revised list of habitable zone candidates, and find that the ages of single and multiple transiting planet systems are statistically indistinguishable.
- ID:
- ivo://CDS.VizieR/J/AJ/159/280
- Title:
- Gaia-Kepler stellar properties catalog.I. KIC stars
- Short Name:
- J/AJ/159/280
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- An accurate and precise Kepler Stellar Properties Catalog is essential for the interpretation of the Kepler exoplanet survey results. Previous Kepler Stellar Properties Catalogs have focused on reporting the best-available parameters for each star, but this has required combining data from a variety of heterogeneous sources. We present the Gaia-Kepler Stellar Properties Catalog, a set of stellar properties of 186301 Kepler stars, homogeneously derived from isochrones and broadband photometry, Gaia Data Release 2 parallaxes, and spectroscopic metallicities, where available. Our photometric effective temperatures, derived from g to Ks colors, are calibrated on stars with interferometric angular diameters. Median catalog uncertainties are 112K for Teff, 0.05dex for logg, 4% for R_*_, 7% for M_*_, 13% for {rho}_*_, 10% for L_*_, and 56% for stellar age. These precise constraints on stellar properties for this sample of stars will allow unprecedented investigations into trends in stellar and exoplanet properties as a function of stellar mass and age. In addition, our homogeneous parameter determinations will permit more accurate calculations of planet occurrence and trends with stellar properties.
1268. Gaia photometry
- ID:
- ivo://CDS.VizieR/J/A+A/523/A48
- Title:
- Gaia photometry
- Short Name:
- J/A+A/523/A48
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The scientific community needs to be prepared to analyse the data from Gaia, one of the most ambitious ESA space missions, which is to be launched in 2012. The purpose of this paper is to provide data and tools to predict how Gaia photometry is expected to be. To do so, we provide relationships among colours involving Gaia magnitudes (white light G, blue GBP, red GRP and GRVS bands) and colours from other commonly used photometric systems (Johnson-Cousins, SDSS, Hipparcos and Tycho). The most up-to-date information from industrial partners has been used to define the nominal passbands, and based on the BaSeL3.1 stellar spectral energy distribution library, relationships were obtained for stars with different reddening values, ranges of temperatures, surface gravities and metallicities. The transformations involving Gaia and Johnson-Cousins V-I_C_ and SDSS g-z colours have the lowest residuals. A polynomial expression for the relation between the effective temperature and the colour G_BP_-G_RP_ was derived for stars with Teff higher than 4500K. For stars with Teff smaller than 4500K, dispersions exist in gravity and metallicity for each absorption value in g-r and r-i. Transformations involving two Johnson or two SDSS colours yield lower residuals than using only one colour. We also computed several ratios of total-to-selective absorption including absorption A_G_ in the G band and colour excess E(G_BP_-G_RP_) for our sample stars. A relationship involving A_G_/A_V_ and the intrinsic (V-I_C_) colour is provided. The derived Gaia passbands have been used to compute tracks and isochrones using the Padova and BASTI models, and the passbands have been included in both web sites. Finally, the performances of the predicted Gaia magnitudes have been estimated according to the magnitude and the celestial coordinates of the star. The provided dependencies among colours can be used for planning scientific exploitation of Gaia data, performing simulations of the Gaia-like sky, planning ground-based complementary observations and for building catalogues with auxiliary data for the Gaia data processing and validation.
- ID:
- ivo://CDS.VizieR/J/A+A/565/A11
- Title:
- Gaia photometry for white dwarfs
- Short Name:
- J/A+A/565/A11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Gaia space mission, through its 5-6 years survey of the whole sky up to magnitude V=20-25, will drastically increase the sample of known white dwarfs allowing to address new science questions. In this paper we provide a characterisation of Gaia photometry for the case of white dwarfs to better prepare for the analysis of the scientific output of the mission including relationships among colours involving Gaia magnitudes (white light G, blue GBP, red GRP and GRVS passbands) and colours from other commonly used photometric systems (Johnson-Cousins, SDSS and 2MASS). We also present numbers of white dwarfs predicted by the Gaia Universe Model Snapshot and compare them with an alternative simulation calibrated with the local white dwarfs sample. In these online tables we provide the values used to fit the relationships in the paper, especially useful for those cases where the deviation from the established relationships is large. The most recent Gaia transmission curves and three different compositions for white dwarfs were considered here (pure hydrogen, pure helium and mixed composition with H/He=0.1).
- ID:
- ivo://CDS.VizieR/I/343
- Title:
- Gaia-PS1-SDSS (GPS1) proper motion catalog
- Short Name:
- I/343
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We combine Gaia DR1, PS1, Sloan Digital Sky Survey (SDSS), and 2MASS astrometry to measure proper motions for 350 million sources across three-fourths of the sky down to a magnitude of m_r_~20. Using positions of galaxies from PS1, we build a common reference frame for the multi-epoch PS1, single-epoch SDSS and 2MASS data, and calibrate the data in small angular patches to this frame. As the Gaia DR1 excludes resolved galaxy images, we choose a different approach to calibrate its positions to this reference frame: we exploit the fact that the proper motions of stars in these patches are linear. By simultaneously fitting the positions of stars at different epochs of-Gaia DR1, PS1, SDSS, and 2MASS-we construct an extensive catalog of proper motions dubbed GPS1. GPS1 has a characteristic systematic error of less than 0.3mas/yr and a typical precision of 1.5-2.0mas/yr. The proper motions have been validated using galaxies, open clusters, distant giant stars, and QSOs. In comparison with other published faint proper motion catalogs, GPS1's systematic error (<0.3mas/yr) should be nearly an order of magnitude better than that of PPMXL and UCAC4 (>2.0mas/yr). Similarly, its precision (~1.5mas/yr) is a four-fold improvement relative to PPMXL and UCAC4 (~6.0mas/yr). For QSOs, the precision of GPS1 is found to be worse (~2.0-3.0mas/yr), possibly due to their particular differential chromatic refraction.
