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1561. Metallicities in the Geneva photometric system
ID:
ivo://CDS.VizieR/J/MNRAS/469/3042
Title:
Metallicities in the Geneva photometric system
Short Name:
J/MNRAS/469/3042
Date:
21 Oct 2021
Publisher:
CDS
Description:
We use the most homogeneous Geneva seven-colour photometric system to derive new metallicity calibrations for early A- to K-type stars that cover both, dwarf stars and giants. The calibrations are based on several spectroscopic data sets that were merged to a common scale, and we applied them to open cluster data to obtain an additional proof of the metallicity scale and accuracy. In total, metallicities of 54 open clusters are presented. The accuracy of the calibrations for single stars is in general below 0.1dex, but for the open cluster sample with mean values based on several stars we find a much better precision, a scatter as low as about 0.03dex. Furthermore, we combine the new results with another comprehensive photometric data set to present a catalogue of mean metallicities for more than 3000 F- and G-type dwarf stars with sigma about 0.06dex. The list was extended by more than 1200 hotter stars up to about 8500K (or spectral type A3) by taking advantage of their almost reddening free characteristic in the new Geneva metallicity calibrations. These two large samples are well suited as primary or secondary calibrators of other data, and we already identified about 20 spectroscopic data sets that show offsets up to about 0.4dex.
1562. Metallicities of damped Ly{alpha} systems
ID:
ivo://CDS.VizieR/J/ApJ/755/89
Title:
Metallicities of damped Ly{alpha} systems
Short Name:
J/ApJ/755/89
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present chemical abundance measurements for 47 damped Ly{alpha} (DLA) systems, 30 at z>4, observed with the Echellette Spectrograph and Imager and the High Resolution Echelle Spectrometer on the Keck telescopes. H I column densities of the DLAs are measured with Voigt profile fits to the Ly{alpha} profiles, and we find an increased number of false DLA identifications with Sloan Digital Sky Survey at z>4 due to the increased density of the Ly{alpha} forest. Ionic column densities are determined using the apparent optical depth method, and we combine our new metallicity measurements with 195 from previous surveys to determine the evolution of the cosmic metallicity of neutral gas. We find the metallicity of DLAs decreases with increasing redshift, improving the significance of the trend and extending it to higher redshifts, with a linear fit of -0.22+/-0.03 dex per unit redshift from z=0.09-5.06. The metallicity "floor" of {approx}1/600 solar continues out to z~5, despite our sensitivity for finding DLAs with much lower metallicities. However, this floor is not statistically different from a steep tail to the distribution. We also find that the intrinsic scatter of metallicity among DLAs of ~0.5dex continues out to z~5. In addition, the metallicity distribution and the {alpha}/Fe ratios of z>2 DLAs are consistent with being drawn from the same parent population with those of halo stars. It is therefore possible that the halo stars in the Milky Way formed out of gas that commonly exhibits DLA absorption at z>2.
1563. Metallicities of Pristine stars
ID:
ivo://CDS.VizieR/J/MNRAS/472/2963
Title:
Metallicities of Pristine stars
Short Name:
J/MNRAS/472/2963
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Pristine survey is a narrow-band, photometric survey focused around the wavelength region of the CaII H&K absorption lines, designed to efficiently search for extremely metal-poor stars. In this work, we use the first results of a medium-resolution spectroscopic follow-up to refine the selection criteria for finding extremely metal-poor stars ([Fe/H]<=-3.0) in the Pristine survey. We consider methods by which stars can be selected from available broad-band and infrared photometry plus the additional Pristine narrow-band photometry. The sample consists of 205 stars in the magnitude range 14<V<18. Applying the photometric selection criteria cuts the sample down to 149 stars, and from these we report a success rate of 70 per cent for finding stars with [Fe/H]<=-2.5 and 22 per cent for finding stars with [Fe/H]<=-3.0. These statistics compare favourably with other surveys that search for extremely metal-poor stars, namely an improvement by a factor of ~4-5 for recovering stars with [Fe/H]<=-3.0. In addition, Pristine covers a fainter magnitude range than its predecessors and can thus probe deeper into the Galactic halo.
1564. Metallicity calibrations for UBV photometry
ID:
ivo://CDS.VizieR/J/MNRAS/371/1793
Title:
Metallicity calibrations for UBV photometry
Short Name:
J/MNRAS/371/1793
Date:
21 Oct 2021
Publisher:
CDS
Description:
Calibrations are presented here for metallicity ([Fe/H]) in terms of the ultraviolet excess, [{Delta}(U-B) at B-V=0.6, hereafter D0.6], and also for the absolute visual magnitude (M_V_) and its difference with respect to the Hyades ({Delta}M^H^_V_) in terms of D0.6 and (B-V), making use of high-resolution spectroscopic abundances from the literature and Hipparcos parallaxes.
1565. Metallicity of bulge clump giants in Baade's window
ID:
ivo://CDS.VizieR/J/A+A/534/A80
Title:
Metallicity of bulge clump giants in Baade's window
Short Name:
J/A+A/534/A80
Date:
21 Oct 2021
Publisher:
CDS
Description:
We seek to constrain the formation of the Galactic bulge by means of analysing the detailed chemical composition of a large sample of red clump stars in Baade's window. These stars were selected to minimise the contamination by other Galactic components, so they are good tracers of the bulge metallicity distribution in Baade's window, at least for stars more metal-rich than ~-1.5. We used an automatic procedure to measure [Fe/H] in a sample of 219 bulge red clump stars from R=20000 resolution spectra obtained with FLAMES/GIRAFFE at the VLT. The analysis was performed differentially with respect to the metal-rich local reference star MuLeo. For a subsample of 162 stars, we also derived [Mg/H] from spectral synthesis around the MgI triplet at 6319{AA}. The Fe and Mg metallicity distributions are both asymmetric with median values of +0.16 and +0.21, respectively. They show only a small proportion of stars at low metallicities, extending down to [Fe/H]=-1.1 or [Mg/H]=-0.7 The iron distribution is clearly bimodal, as revealed both by a deconvolution (from observational errors) and a Gaussian decomposition. The decomposition of the observed Fe and Mg metallicity distributions into Gaussian components yields two populations of equal sizes (50% each): a metal-poor component centred on [Fe/H]=-0.30 and [Mg/H]=-0.06 with a large dispersion and a narrow metal-rich component centred on [Fe/H]=+0.32 and [Mg/H]=+0.35. The metal-poor component shows high [Mg/Fe] ratios (around 0.3), while stars in the metal-rich component are found to have near solar ratios. Kinematical differences between the two components have also been found: the metal-poor component shows kinematics compatible with an old spheroid, while the metal-rich component is consistent with a population supporting a bar. In view of their chemical and kinematical properties, we suggest different formation scenarii for the two populations: a rapid formation time scale as an old spheroid for the metal-poor component (old bulge) and for the metal-rich component, a formation on a longer time scale driven by the evolution of the bar (pseudo-bulge).
1566. Metallicity of RGB stars in 6 M31 dwarf galaxies
ID:
ivo://CDS.VizieR/J/ApJ/798/77
Title:
Metallicity of RGB stars in 6 M31 dwarf galaxies
Short Name:
J/ApJ/798/77
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present global metallicity properties, metallicity distribution functions (MDFs), and radial metallicity profiles for the six most luminous M31 dwarf galaxy satellites: M32, NGC 205, NGC 185, NGC 147, Andromeda VII, and Andromeda II. The results presented are the first spectroscopic MDFs for dwarf systems surrounding a host galaxy other than the Milky Way (MW). Our sample consists of individual metallicity measurements for 1243 red giant branch member stars spread across these six systems. We determine metallicities based on the strength of the Ca II triplet lines using the empirical calibration of Carrera et al. (2013, J/MNRAS/434/1681), which is calibrated over the metallicity range -4<[Fe/H]<+0.5. We find that these M31 satellites lie on the same luminosity-metallicity relationship as the MW dwarf satellites. We do not find a trend between the internal metallicity spread and galaxy luminosity, contrary to previous studies. The MDF widths of And II and And VII are similar to the MW dwarf spheroidal (dSph) satellites of comparable luminosity; however, our four brightest M31 dwarf satellites are more luminous than any of the MW dSphs and have broader MDFs. The MDFs of our six M31 dwarf satellites are consistent with the leaky box model of chemical evolution, although our metallicity errors allow a wide range of evolution models. We find a significant radial gradient in metallicity in only two of our six systems, NGC 185 and Andromeda II, and flat radial metallicity gradients in the rest of our sample with no observed correlation between rotational support and radial metallicity gradients. Although the average properties and radial trends of the M31 dwarf galaxies agree with their MW counterparts at similar luminosity, the detailed MDFs are different, particularly at the metal-rich end.
1567. Metal-poor MS stars UBV photometry
ID:
ivo://CDS.VizieR/J/AJ/108/538
Title:
Metal-poor MS stars UBV photometry
Short Name:
J/AJ/108/538
Date:
21 Oct 2021
Publisher:
CDS
Description:
From analysis of a photometrically selected sample of 175 metal-poor field stars with main sequence gravities (hereafter BMPs) and UBV colors blueward of the most metal-poor globular cluster main-sequence turnoffs, 0.15<(B-V)_0_<0.35, and properties of the candidate lists of the HK objective prism survey, we calculate the space density and a suitably defined specific frequency of BMPs within ~2kpc of the Sun. We consider two cases. If we adopt the luminosities and color distribution of globular cluster blue stragglers (hereafter BS) for BMPs, the BMP space density, is ~350kpc^-3^, from which we obtain a specific frequency S(BMP)~8, a value 9 times larger than that of BSs in globular clusters. From this result, we conclude that cluster-type BSs are but a minor component of the field BMPs and that the remainder must be of a different nature. If we adopt luminosities of metal-poor models halfway between the Zero Age Main Sequence and the phase of core hydrogen exhaustion, we obtain a space density of 450(+300,-150)kpc^-3^ and a specific frequency S(BMP)=10(+5,-3). From a subsample of 107 BMPs with available radial velocities we derive a galactic rotation of 128km/s and an isotropic velocity dispersion of {sigma}~90km/s, values intermediate between those of halo and thick-disk populations. From analysis of a larger sample of stars on 0.15<(B-V)0<0.35 binned by a crude line-blanketing parameter, we find that our results are insensitive to adopted BMP selection criteria: none of these subsamples of A- and early F-type stars above the galactic plane possess disk kinematics. The region of the UBV two-color diagram occupied by BMPs could be populated by metal-deficient, main-sequence gravity stars with ages substantially younger than those of the metal-poor halo. Because we cannot imagine how or where the observed local population of BMPs could have been produced within our galaxy during the past 3 to 10Gyr, we suggest that BMPs are the bluest members of metal-poor intermediate-age main sequences accreted, probably, from dwarf spheroidal satellites of the Milky Way during the past 10Gyr. We discuss observational consequences of this suggestion.
1568. Metal-poor solar-type stars spectroscopy and masses
ID:
ivo://CDS.VizieR/J/A+A/526/A99
Title:
Metal-poor solar-type stars spectroscopy and masses
Short Name:
J/A+A/526/A99
Date:
21 Oct 2021
Publisher:
CDS
Description:
Stellar metallicity strongly correlates with the presence of planets and their properties. To check for new correlations between stars and the existence of an orbiting planet, we determine precise stellar parameters for a sample of metal-poor solar-type stars. This sample was observed with the HARPS spectrograph and is part of a program to search for new extrasolar planets.
1569. Metal-poor stars in the thick disk of the Galaxy
ID:
ivo://CDS.VizieR/J/ApJ/794/58
Title:
Metal-poor stars in the thick disk of the Galaxy
Short Name:
J/ApJ/794/58
Date:
21 Oct 2021
Publisher:
CDS
Description:
A new set of very high signal-to-noise (S/N>100/1), medium-resolution (R~3000) optical spectra have been obtained for 302 of the candidate "weak-metal" stars selected by Bidelman & MacConnell (1973AJ.....78..687B, Cat. III/46). We use these data to calibrate the recently developed generalization of the Sloan Extension for Galactic Exploration and Understanding and Exploration (SEGUE) Stellar Parameter Pipeline, and obtain estimates of the atmospheric parameters (T_eff_, log g, and [Fe/H]) for these non-Sloan Digital Sky Survey/SEGUE data; we also obtain estimates of [C/Fe]. The new abundance measurements are shown to be consistent with available high-resolution spectroscopic determinations, and represent a substantial improvement over the accuracies obtained from the previous photometric estimates reported in Paper I of this series (Norris et al. 1985ApJS...58..463N). The apparent offset in the photometric abundances of the giants in this sample noted by several authors is confirmed by our new spectroscopy; no such effect is found for the dwarfs. The presence of a metal-weak thick-disk (MWTD) population is clearly supported by these new abundance data. Some 25% of the stars with metallicities -1.8<[Fe/H]<=-0.8 exhibit orbital eccentricities e<0.4, yet are clearly separated from members of the inner-halo population with similar metallicities by their location in a Lindblad energy versus angular momentum diagram. A comparison is made with recent results for a similar-size sample of Radial Velocity Experiment stars from Ruchti et al. (2010ApJ...721L..92R ; 2011ApJ...737....9R). We conclude, based on both of these samples, that the MWTD is real, and must be accounted for in discussions of the formation and evolution of the disk system of the Milky Way.
1570. Metal-poor stars uvby-beta photometry. XI.
ID:
ivo://CDS.VizieR/J/A+A/445/939
Title:
Metal-poor stars uvby-beta photometry. XI.
Short Name:
J/A+A/445/939
Date:
21 Oct 2021
Publisher:
CDS
Description:
New uvby-beta data are provided for 442 high-velocity and metal-poor stars; 90 of these stars have been observed previously by us, and 352 are new. When combined with our previous two photometric catalogues, the data base is now made up of 1533 high-velocity and metal-poor stars, all with photometry and complete kinematic data. Hipparcos, plus a new photometric calibration for M_v_ also based on the Hipparcos parallaxes, provide distances for nearly all of these stars; our previous photometric calibrations give values for E(b-y) and [Fe/H]. The [Fe/H],V(rot) diagram allows us to separate these stars into different Galactic stellar population groups, such as old-thin-disk, thick-disk, and halo. The X histogram, where X is our stellar-population discriminator combining V(rot) and [Fe/H], and contour plots for the [Fe/H],V(rot) diagram both indicate two probable components to the thick disk.