- ID:
- ivo://CDS.VizieR/J/AJ/140/1911
- Title:
- Astrometric Grid Giant Star Survey. III.
- Short Name:
- J/AJ/140/1911
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of high-resolution (~55000) spectral observations of 830 photometrically pre-selected candidate red giants in the magnitude range of V=9-12. We develop a pipeline for automated determination of the stellar atmospheric parameters from these spectra and estimate Teff, logg, [Fe/H], microturbulence velocity, and projected rotational velocities, vsin i, for the stars. The analysis confirms that the candidate selection procedure yielded red giants with very high success rate. We show that most of these stars are G and K giants with slightly subsolar metallicity ([Fe/H]~-0.3dex). An analysis of Mg abundances in the sample results in consistency of the [Mg/Fe] vs [Fe/H] trend with published results.
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Search Results
- ID:
- ivo://CDS.VizieR/J/PAZh/38/571
- Title:
- Astrophysical parameters for 593 open clusters
- Short Name:
- J/PAZh/38/571
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Based on published data, we have compiled a catalogue of fundamental astrophysical parameters for 593 open clusters of the Galaxy. In particular, the catalogue provides the Galactic orbital elements for 500 clusters, the masses, central concentrations, and ellipticities for 424 clusters, the metallicities for 264 clusters, and the relative magnesium abundances for 56 clusters. We describe the sources of initial data and estimate the errors in the investigated parameters. The selection effects are discussed. The chemical and kinematical properties of the open clusters and field thin-disk stars are shown to differ. We provide evidence for the heterogeneity of the population of open star clusters.
- ID:
- ivo://CDS.VizieR/J/AJ/127/1567
- Title:
- Asymmetric thick disk. II. Kinematics
- Short Name:
- J/AJ/127/1567
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report a kinematic signature associated with the observed asymmetry in the distribution of thick-disk/inner halo stars interior to the solar circle described in Paper I (Parker et al., 2003AJ....126.1346P). In that paper, we found a statistically significant excess (20%-25%) of stars in quadrant I (l~20{deg}-55{deg}) both above and below the plane (b~+/-25{deg} to b~+/-45{deg}) compared with the complementary region in quadrant IV. We have measured Doppler velocities for 741 stars, selected according to the same magnitude and color criteria, in the direction of the asymmetry and in the corresponding fields in quadrant IV. We have also determined spectral types and metallicities measured from the same spectra.
- ID:
- ivo://CDS.VizieR/J/A+A/619/A134
- Title:
- ATHOS. Flux ratio based stellar parameterization
- Short Name:
- J/A+A/619/A134
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The rapidly increasing number of stellar spectra obtained by existing and future large-scale spectroscopic surveys feeds a demand for fast and efficient tools for the spectroscopic determination of fundamental stellar parameters. Such tools should not only comprise customized solutions for one particular survey or instrument, but, in order to enable cross-survey comparability, they should also be capable of dealing with spectra from a variety of spectrographs, resolutions, and wavelength coverages. To meet these ambitious specifications, we developed ATHOS (A Tool for HOmogenizing Stellar parameters), a fundamentally new analysis tool that adopts easy-to-use, computationally inexpensive analytical relations tying flux ratios (FRs) of designated wavelength regions in optical spectra to the stellar parameters effective temperature (Teff), iron abundance ([Fe/H]), and surface gravity (logg). Our Teff estimator is based on FRs from nine pairs of wavelength ranges around the Balmer lines H{beta} and H{alpha}, while for [Fe/H] and logg we provide 31 and 11 FRs, respectively, which are spread between ~4800{AA} and ~6500{AA}; a region covered by most optical surveys. The analytical relations employing these FRs were trained on N=124 real spectra of a stellar benchmark sample that covers a large parameter space of Teff~=4000 to 6500K (spectral types F to K), [Fe/H]~=-4.5 to 0.3dex, and logg~=1 to 5dex, which at the same time reflects ATHOS' range of applicability. We find accuracies of 97K for Teff, 0.16dex for [Fe/H], and 0.26dex for logg, which are merely bounded by finite uncertainties in the training sample parameters. ATHOS' internal precisions can be better by up to 70%. We tested ATHOS on six independent large surveys spanning a wide range of resolutions (R~=2000 to 52000), amongst which are the Gaia-ESO and the SDSS/SEGUE surveys. The exceptionally low execution time (<30ms per spectrum per CPU core) together with a comparison to the literature parameters showed that ATHOS can successfully achieve its main objectives, in other words fast stellar parametrization with cross-survey validity, high accuracy, and high precision. These are key to homogenize the output from future surveys, such as 4MOST or WEAVE.
265. ATLAS3D Project. XXX
- ID:
- ivo://CDS.VizieR/J/MNRAS/448/3484
- Title:
- ATLAS3D Project. XXX
- Short Name:
- J/MNRAS/448/3484
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the stellar population content of early-type galaxies from the ATLAS3D survey. Using spectra integrated within apertures covering up to one effective radius, we apply two methods: one based on measuring line-strength indices and applying single stellar population (SSP) models to derive SSP-equivalent values of stellar age, metallicity, and alpha enhancement; and one based on spectral fitting to derive non-parametric star formation histories, mass-weighted average values of age, metallicity, and half-mass formation time-scales. Using homogeneously derived effective radii and dynamically determined galaxy masses, we present the distribution of stellar population parameters on the Mass Plane (M_JAM_, {sigma}_e_, R^maj^_e_), showing that at fixed mass, compact early-type galaxies are on average older, more metal-rich, and more alpha-enhanced than their larger counterparts. From non-parametric star formation histories, we find that the duration of star formation is systematically more extended in lower mass objects. Assuming that our sample represents most of the stellar content of today's local Universe, approximately 50 percent of all stars formed within the first 2Gyr following the big bang. Most of these stars reside today in the most massive galaxies (>10^10.5^M_{sun}_), which themselves formed 90 percent of their stars by z~2. The lower mass objects, in contrast, have formed barely half their stars in this time interval. Stellar population properties are independent of environment over two orders of magnitude in local density, varying only with galaxy mass. In the highest density regions of our volume (dominated by the Virgo cluster), galaxies are older, alpha-enhanced, and have shorter star formation histories with respect to lower density regions.
- ID:
- ivo://CDS.VizieR/J/A+A/635/A129
- Title:
- ATLAS^3D^ sample metallicity and age gradients
- Short Name:
- J/A+A/635/A129
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the evidence for a diversity of formation processes in early-type galaxies by presenting the first complete volume-limited sample of slow rotators with both integral-field kinematics from the ATLAS^3D^ Project and high spatial resolution photometry from the Hubble Space Telescope. Analysing the nuclear surface brightness profiles of 12 newly imaged slow rotators, we classify their light profiles as core-less, and place an upper limit to the core size of about 10 pc. Considering the full magnitude and volume-limited ATLAS^3D^ sample, we correlate the presence or lack of cores with stellar kinematics, including the proxy for the stellar angular momentum ({lambda}_Re_) and the velocity dispersion within one half-light radius ({sigma}_e_), stellar mass, stellar age, {alpha}-element abundance, and age and metallicity gradients. More than half of the slow rotators have core-less light profiles, and they are all less massive than 10^11^M_{sun}_. Core-less slow rotators show evidence for counter-rotating flattened structures, have steeper metallicity gradients, and a larger dispersion of gradient values ({Delta}[Z/H]=-0.42+/-0.18) than core slow rotators ({Delta}[Z/H]=-0.23+/-0.07). Our results suggest that core and core-less slow rotators have different assembly processes, where the former, as previously discussed, are the relics of massive dissipation-less merging in the presence of central supermassive black holes. Formation processes of core-less slow rotators are consistent with accretion of counter-rotating gas or gas-rich mergers of special orbital configurations, which lower the final net angular momentum of stars, but support star formation. We also highlight core fast rotators as galaxies that share properties of core slow rotators (i.e. cores, ages, {sigma}_e_, and population gradients) and core-less slow rotators (i.e. kinematics, {lambda}_Re_, mass, and larger spread in population gradients). Formation processes similar to those for core-less slow rotators can be invoked to explain the assembly of core fast rotators, with the distinction that these processes form or preserve cores.
- ID:
- ivo://CDS.VizieR/J/A+A/611/A6
- Title:
- ATLASGAL massive clumps H_2_CO data
- Short Name:
- J/A+A/611/A6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Formaldehyde (H_2_CO) is a reliable tracer to accurately measure the physical parameters of dense gas in star-forming regions. We aim to determine directly the kinetic temperature and spatial density with formaldehyde for the ~100 brightest ATLASGAL-selected clumps (the TOP100 sample) at 870um representing various evolutionary stages of high-mass star formation. Ten transitions (J=3-2 and 4-3) of ortho- and para-H2CO near 211, 218, 225, and 291GHz were observed with the Atacama Pathfinder EXperiment (APEX) 12m telescope.
- ID:
- ivo://CDS.VizieR/J/A+A/616/A112
- Title:
- Atmospheric param. & abundances of red giants
- Short Name:
- J/A+A/616/A112
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recent observational results have demonstrated an increase in the surface Na abundance that correlates with stellar mass for red giants between 2 and 3M_{sun}_. This trend supports evolutionary mixing processes as the explanation for Na overabundances seen in some red giants. In this same mass range, the surface Al abundance was shown to be constant. Our main aim was to extend the investigation of the Na and Al surface abundances to giants more massive than 3M_{sun}_. We sought to establish accurately whether the Na abundances keep increasing with stellar mass or a plateau is reached. In addition, we investigated whether mixing can affect the surface abundance of Al in giants more massive than 3M_{sun}_. We obtained new high-resolution spectra of 20 giants in the field of 10 open clusters; 17 of these stars were found to be members of 9 clusters. The giants have masses between 2.5M_{sun}_ and 5.6M_{sun}_. A model atmosphere analysis was performed and abundances of up to 22 elements were derived using equivalent widths. Additionally, abundances of C, N, and O were determined using spectrum synthesis. The abundances of Na and Al were corrected for non-local thermodynamic equilibrium (non-LTE) effects. Moreover, to extend the mass range of our sample, we collected from the literature high-quality C, N, O, and Na abundances of 32 Galactic Cepheids with accurate masses in the range between 3M_{sun}_ and 14M_{sun}_. The surface abundances of C, N, O, Na, and Al were compared to predictions of stellar evolution models with and without the inclusion of rotation-induced mixing. The surface abundances of most giants and Cepheids of the sample can be explained by models without rotation. For giants above ~2.5M_{sun}_, the Na abundances reach a plateau level of about [Na/Fe]~0.20-0.25dex (in non-LTE). This is true for both Cepheids and giants in open clusters. Regarding Al, the non-LTE [Al/Fe] ratios are mostly close to solar and suggest that Al is not affected by the first dredge-up up to ~5.0M_{sun}_. Our results support previous works that found models with rotation to overestimate the mixing effects in intermediate-mass stars.
- ID:
- ivo://CDS.VizieR/J/other/RAA/11.924
- Title:
- Atmospheric parameters for 771 stars
- Short Name:
- J/other/RAA/11.9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A number of spectroscopic surveys have been carried out or are planned to study the origin of the Milky Way. Their exploitation requires reliable automated methods and softwares to measure the fundamental parameters of the stars. Adopting the ULySS package, we have tested the effect of different resolutions and signal-to-noise ratios (SNR) on the measurement of the stellar atmospheric parameters (effective temperature Teff, surface gravity logg, and metallicity [Fe/H]). We show that ULySS is reliable to determine these parameters with medium-resolution spectra (R~2000). Then, we applied the method to measure the parameters of 771 stars selected in the commissioning database of the Guoshoujing Telescope (GSJT). The results were compared with the SDSS/SEGUE Stellar Parameter Pipeline (SSPP), and we derived precisions of 167K, 0.34dex, and 0.16dex for Teff, logg and [Fe/H] respectively. Furthermore, 120 of these stars are selected to construct the primary stellar spectra template library (Version 1.0) of GSJT, and will be deployed as basic ingredients for the GSJT automated parametrization pipeline.
- ID:
- ivo://CDS.VizieR/J/A+A/525/A71
- Title:
- Atmospheric parameters for 1273 stars
- Short Name:
- J/A+A/525/A71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Empirical libraries of stellar spectra play an important role in different fields. For example, they are used as reference for the automatic determination of atmospheric parameters, or for building synthetic stellar populations to study galaxies. The CFLIB (Coude-feed library, Indo-US) database is at present one of the most complete libraries, in terms of its coverage of the atmospheric parameters space (Teff, logg and [Fe/H]) and wavelength coverage 3460-9464{AA} at a resolution of ~1{AA} FWHM. Although the atmospheric parameters of most of the stars were determined from detailed analyses of high-resolution spectra, for nearly 300 of the 1273 stars of the library at least one of the three parameters is missing. For the others, the measurements, compiled from the literature, are inhomogeneous. In this paper, we re-determine the atmospheric parameters, directly using the CFLIB spectra, and compare them to the previous studies. Methods. We use the ULySS program to derive the atmospheric parameters, using the ELODIE library as a reference. Based on comparisons with several previous studies we conclude that our determinations are unbiased. For the 958 F,G, and K type stars the precision on Teff, logg, and [Fe/H] is respectively 43K, 0.13dex and 0.05dex. For the 53 M stars they are 82K, 0.22dex and 0.28dex. And for the 260 OBA type stars the relative precision on Teff is 5.1%, and on logg, and [Fe/H] the precision is respectively 0.19 dex and 0.16 dex. These parameters will be used to re-calibrate the CFLIB fluxes and to produce synthetic spectra of stellar populations.
