- ID:
- ivo://CDS.VizieR/J/MNRAS/475/3633
- Title:
- Mass and age of red giant branch stars
- Short Name:
- J/MNRAS/475/3633
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Obtaining accurate and precise masses and ages for large numbers of giant stars is of great importance for unraveling the assemblage history of the Galaxy. In this paper, we estimate masses and ages of 6940 red giant branch (RGB) stars with asteroseismic parameters deduced from Kepler photometry and stellar atmospheric parameters derived from LAMOST spectra. The typical uncertainties of mass is a few per cent, and that of age is ~20 per cent. The sample stars reveal two separate sequences in the age-[{alpha}/Fe] relation - a high-{alpha} sequence with stars older than ~8Gyr and a low-{alpha} sequence composed of stars with ages ranging from younger than 1Gyr to older than 11Gyr. We further investigate the feasibility of deducing ages and masses directly from LAMOST spectra with a machine learning method based on kernel based principal component analysis, taking a sub-sample of these RGB stars as a training data set. We demonstrate that ages thus derived achieve an accuracy of ~24 per cent. We also explored the feasibility of estimating ages and masses based on the spectroscopically measured carbon and nitrogen abundances. The results are quite satisfactory and significantly improved compared to the previous studies.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/349/757
- Title:
- Masses, ages and metallicities of F-G dwarfs
- Short Name:
- J/MNRAS/349/757
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Lithium abundances are presented for a total of 451 F-G dwarfs. The aim of this survey of Lithium abundance is to document the astration of Li as a function of stellar mass, age, and metallicity. These data are given in table1.dat, which includes 157 stars for which the Li abundance is determined for the first time. Almost all stars belonging to thin disc population.
- ID:
- ivo://CDS.VizieR/J/ApJ/695/259
- Title:
- Massive metal-poor galaxies from SDSS
- Short Name:
- J/ApJ/695/259
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a sample of 42 high-mass low-metallicity outliers from the mass-metallicity relation of star-forming galaxies. These galaxies have stellar masses that span log(M_*_/M_{sun}_)~9.4 to 11.1 and are offset from the mass-metallicity relation by -0.3 to -0.85dex in 12+log(O/H). In general, they are extremely blue, have high star-formation rates for their masses, and are morphologically disturbed. Tidal interactions are expected to induce large-scale gas inflow to the galaxies' central regions, and we find that these galaxies' gas-phase oxygen abundances are consistent with large quantities of low-metallicity gas from large galactocentric radii diluting the central metal-rich gas. We conclude with implications for deducing gas-phase metallicities of individual galaxies based solely on their luminosities, specifically in the case of long gamma-ray burst host galaxies.
- ID:
- ivo://CDS.VizieR/J/ApJ/874/66
- Title:
- MASSIVE survey. XII. Early-type galaxy gradients
- Short Name:
- J/ApJ/874/66
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We measure the stellar populations as a function of the radius for 90 early-type galaxies (ETGs) in the MASSIVE survey, a volume-limited integral-field spectroscopic (IFS) galaxy survey targeting all northern-sky ETGs with an absolute K-band magnitude of M_K_{<}-25.3mag or a stellar mass of M_*_>~4x10^11^M_{sun}_, within 108Mpc. We are able to measure reliable stellar population parameters for individual galaxies out to 10-20kpc (1-3R_e_) depending on the galaxy. Focusing on ~R_e_ (~10kpc), we find significant correlations between the abundance ratios, {sigma}, and M^*^ at a large radius, but we also find that the abundance ratios saturate in the highest-mass bin. We see a strong correlation between the kurtosis of the line-of-sight velocity distribution (h4) and the stellar population parameters beyond R_e_. Galaxies with higher radial anisotropy appear to be older, with metal-poorer stars and enhanced [{alpha}/Fe]. We suggest that the higher radial anisotropy may derive from more accretion of small satellites. Finally, we see some evidence for correlations between environmental metrics (measured locally and on >5Mpc scales) and the stellar populations, as expected if satellites are quenched earlier in denser environments.
- ID:
- ivo://CDS.VizieR/J/ApJ/850/179
- Title:
- 2MASS J15111324-2130030 metal-poor star abundances
- Short Name:
- J/ApJ/850/179
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The rapid neutron-capture or r-process is thought to produce the majority of the heavy elements (Z>30) in extremely metal-poor stars. The same process is also responsible for a significant fraction of the heavy elements in the Sun. This universality of the r-process is one of its characteristic features, as well as one of the most important clues to its astrophysical origin. We report the discovery of an extremely metal-poor field giant with [Sr,Ba/H]~-6.0 and [Sr,Ba/Fe]~-3.0, the lowest abundances of strontium and barium relative to iron ever observed. Despite its low abundances, the star 2MASS J151113.24-213003.0 has [Sr/Ba]=-0.11+/-0.14, therefore its neutron-capture abundances are consistent with the main solar r-process pattern that has [Sr/Ba]=-0.25. It has been suggested that extremely low neutron-capture abundances are a characteristic of dwarf galaxies, and we find that this star is on a highly eccentric orbit with an apocenter >~100kpc that lies in the disk of satellites in the halo of the Milky Way. We show that other extremely metal-poor stars with low [Sr,Ba/H] and [Sr,Ba/Fe] plus solar [Sr/Ba] tend to have orbits with large apocenters, consistent with a dwarf galaxy origin for this class of object. The nucleosynthesis event that produced the neutron-capture elements in 2MASS J151113.24-213003.0 must produce both strontium and barium together in the solar ratio. We exclude contributions from the s-process in intermediate-mass asymptotic giant branch or fast-rotating massive metal-poor stars, pair-instability supernovae, the weak r-process, and neutron-star mergers. We argue that the event was a Pop III or extreme Pop II core-collapse supernova explosion.
- ID:
- ivo://CDS.VizieR/J/ApJ/831/64
- Title:
- Mass-metallicity relation for giant planets
- Short Name:
- J/ApJ/831/64
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Exoplanet discoveries of recent years have provided a great deal of new data for studying the bulk compositions of giant planets. Here we identify 47 transiting giant planets (20 M_{\Earth}_ < M < 20 M_J_) whose stellar insolations are low enough (F_*_ < 2 x 10^8^ erg s^-1^ cm^-2^, or roughly T_eff_ < 1000) that they are not affected by the hot-Jupiter radius inflation mechanism(s). We compute a set of new thermal and structural evolution models and use these models in comparison with properties of the 47 transiting planets (mass, radius, age) to determine their heavy element masses. A clear correlation emerges between the planetary heavy element mass M_z_ and the total planet mass, approximately of the form M_z_\propto\sqrtM. This finding is consistent with the core-accretion model of planet formation. We also study how stellar metallicity [Fe/H] affects planetary metal-enrichment and find a weaker correlation than has previously been reported from studies with smaller sample sizes. We confirm a strong relationship between the planetary metal-enrichment relative to the parent star Z_planet_/Z_star_ and the planetary mass, but see no relation in Z_planet_/Z_star_ with planet orbital properties or stellar mass. The large heavy element masses of many planets (>50 M_{\Earth}_) suggest significant amounts of heavy elements in H/He envelopes, rather than cores, such that metal-enriched giant planet atmospheres should be the rule. We also discuss a model of core-accretion planet formation in a one-dimensional disk and show that it agrees well with our derived relation between mass and Z_planet_/Z_star_.
- ID:
- ivo://CDS.VizieR/J/MNRAS/469/2121
- Title:
- Mass-metallicity relation revisited with CALIFA
- Short Name:
- J/MNRAS/469/2121
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an updated version of the mass-metallicity (MZ) relation using integral field spectroscopy data obtained from 734 galaxies observed by the CALIFA survey. These unparalleled spatially resolved spectroscopic data allow us to determine the metallicity at the same physical scale (R_e_) for different calibrators. We obtain MZ relations with similar shapes for all calibrators, once the scalefactors among them are taken into account. We do not find any significant secondary relation of the MZ relation with either the star formation rate (SFR) or the specific SFR for any of the calibrators used in this study, based on the analysis of the residuals of the best-fitted relation. However, we do see a hint for an (s)SFR-dependent deviation of the MZ relation at low masses (M<10^9.5^M_{sun}_), where our sample is not complete. We are thus unable to confirm the results by Mannucci et al. (2010), although we cannot exclude that this result is due to the differences in the analysed data sets. In contrast, our results are inconsistent with the results by Lara-Lopez et al. (2010), and we can exclude the presence of an SFR-mass-oxygen abundance fundamental plane. These results agree with previous findings suggesting that either (1) the secondary relation with the SFR could be induced by an aperture effect in single fibre/aperture spectroscopic surveys, (2) it could be related to a local effect confined to the central regions of galaxies or (3) it is just restricted to the low-mass regime, or a combination of the three effects.
- ID:
- ivo://CDS.VizieR/J/ApJ/847/18
- Title:
- Mass, Z, dust attenuation, and SFR relations
- Short Name:
- J/ApJ/847/18
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze the optical continuum of star-forming galaxies in the Sloan Digital Sky Survey by fitting stacked spectra with stellar population synthesis models to investigate the relation between stellar mass, stellar metallicity, dust attenuation, and star formation rate. We fit models calculated with star formation and chemical evolution histories that are derived empirically from multi-epoch observations of the stellar mass-star formation rate and the stellar mass-gas-phase metallicity relations, respectively. We also fit linear combinations of single-burst models with a range of metallicities and ages. Star formation and chemical evolution histories are unconstrained for these models. The stellar mass-stellar metallicity relations obtained from the two methods agree with the relation measured from individual supergiant stars in nearby galaxies. These relations are also consistent with the relation obtained from emission-line analysis of gas-phase metallicity after accounting for systematic offsets in the gas-phase metallicity. We measure dust attenuation of the stellar continuum and show that its dependence on stellar mass and star formation rate is consistent with previously reported results derived from nebular emission lines. However, stellar continuum attenuation is smaller than nebular emission line attenuation. The continuum-to-nebular attenuation ratio depends on stellar mass and is smaller in more massive galaxies. Our consistent analysis of stellar continuum and nebular emission lines paves the way for a comprehensive investigation of stellar metallicities of star-forming and quiescent galaxies.
- ID:
- ivo://CDS.VizieR/J/AJ/141/62
- Title:
- M5 chemical abundances for evolved stars
- Short Name:
- J/AJ/141/62
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present analysis of high-resolution spectra of a sample of stars in the globular cluster M5 (NGC 5904). The sample includes stars from the red giant branch (RGB; seven stars), the red horizontal branch (two stars), and the asymptotic giant branch (AGB; eight stars), with effective temperatures ranging from 4000K to 6100K. Spectra were obtained with the HIRES spectrometer on the Keck I telescope, with a wavelength coverage from 3700{AA} to 7950{AA} for the HB and AGB sample, and 5300{AA} to 7600{AA} for the majority of the RGB sample.
- ID:
- ivo://CDS.VizieR/J/ApJ/802/L10
- Title:
- M dwarf SpeX NIR spectroscopy
- Short Name:
- J/ApJ/802/L10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Despite the ubiquity of M dwarfs and their growing importance to studies of exoplanets, Galactic evolution, and stellar structure, methods for precisely measuring their fundamental stellar properties remain elusive. Existing techniques for measuring M dwarf luminosity, mass, radius, or composition are calibrated over a limited range of stellar parameters or require expensive observations. We find a strong correlation between the K_S_-band luminosity (M_K_), the observed strength of the I-band sodium doublet absorption feature, and [Fe/H] in M dwarfs without strong H{alpha} emission. We show that the strength of this feature, coupled with [Fe/H] and spectral type, can be used to derive M dwarf M_K_ and radius without requiring parallax. Additionally, we find promising evidence that the strengths of the I-band sodium doublet and the nearby I-band calcium triplet may jointly indicate {alpha}-element enrichment. The use of these I-band features requires only moderate-resolution near-infrared spectroscopy to provide valuable information about the potential habitability of exoplanets around M dwarfs, and surface gravity and distance for M dwarfs throughout the Galaxy. This technique has immediate applicability for both target selection and candidate planet-host system characterization for exoplanet missions such as TESS and K2.
