Search

Start Over Content Level Research
591. Age-metallicity relation for nearby stars
ID:
ivo://CDS.VizieR/J/A+A/394/927
Title:
Age-metallicity relation for nearby stars
Short Name:
J/A+A/394/927
Date:
21 Oct 2021
Publisher:
CDS
Description:
Ages, Fe and Ca abundances, orbits, and populations for 1658 solar neighbourhood stars are presented. Stars are selected from Hipparcos (Cat. <II/239> Catalogue.
592. Age-metallicity relation in solar neighbourhood
ID:
ivo://CDS.VizieR/J/A+A/377/911
Title:
Age-metallicity relation in solar neighbourhood
Short Name:
J/A+A/377/911
Date:
21 Oct 2021
Publisher:
CDS
Description:
We derive stellar ages, from evolutionary tracks, and metallicities, from Stroemgren photometry, for a sample of 5828 dwarf and sub-dwarf stars from the Hipparcos (Cat. <I/239>) Catalogue. This stellar disk sample is used to investigate the age-metallicity diagram in the solar neighbourhood. Such diagrams are often used to derive a so called age-metallicity relation. Because of the size of our sample, we are able to quantify the impact on such diagrams, and derived relations, due to different selection effects. Some of these effects are of a more subtle sort, giving rise to erroneous conclusions. In particular we show that [1] the age-metallicity diagram is well populated at all ages and especially that old, metal-rich stars do exist, [2] the scatter in metallicity at any given age is larger than the observational errors, [3] the exclusion of cooler dwarf stars from an age-metallicity sample preferentially excludes old, metal-rich stars, depleting the upper right-hand corner of the age-metallicity diagram, [4] the distance dependence found in the Edvardsson et al. (1993, Cat. <J/A+A/275/101>) sample by Garnett & Kobulnicky (2000ApJ...532.1192G) is an expected artifact due to the construction of the original sample. We conclude that, although some of it can be attributed to stellar migration in the galactic disk, a large part of the observed scatter is intrinsic to the formation processes of stars.
593. Age-metallicity relation of {omega} Cen
ID:
ivo://CDS.VizieR/J/ApJ/647/1075
Title:
Age-metallicity relation of {omega} Cen
Short Name:
J/ApJ/647/1075
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a metallicity distribution based on photometry and spectra for 442 Omega Centauri cluster members that lie at the main-sequence turnoff region of the color-magnitude diagram. This distribution is similar to that found for the red giant branch. The distribution shows a sharp rise to a mean of [Fe/H]=-1.7 with a long tail to higher metallicities. Ages have then been determined for the stars using theoretical isochrones enabling the construction of an age-metallicity diagram. Interpretation of this diagram is complicated by the correlation of the errors in the metallicities and ages. Nevertheless, after extensive Monte Carlo simulations, we conclude that our data show that the formation of the cluster took place over an extended period of time: the most metal-rich stars in our sample ([Fe/H]~-0.6) are younger by 2-4Gyr than the most metal-poor population.
594. Age-metallicity relation via photometry
ID:
ivo://CDS.VizieR/J/MNRAS/385/1270
Title:
Age-metallicity relation via photometry
Short Name:
J/MNRAS/385/1270
Date:
21 Oct 2021
Publisher:
CDS
Description:
Using a widely used stellar-population synthesis model, we study the possibility of using pairs of AB system colours to break the well-known stellar age-metallicity degeneracy and to give constraints on two luminosity-weighted stellar-population parameters (age and metallicity). We present the relative age and metallicity sensitivities of the AB system colours that relate to the u, B, g, V, r, R, i, I, z, J,H and K bands, and we quantify the ability of various colour pairs to break the age-metallicity degeneracy. The results also show that the stellar ages and metallicities of galaxies observed by the Sloan Digital Sky Survey and the Two-Micron All-Sky Survey can be estimated via photometry data.
595. Age of 269 GDR2 open clusters
ID:
ivo://CDS.VizieR/J/A+A/623/A108
Title:
Age of 269 GDR2 open clusters
Short Name:
J/A+A/623/A108
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Gaia Second Data Release provides precise astrometry and photometry for more than 1.3 billion sources. This catalog opens a new era concerning the characterization of open clusters and test stellar models, paving the way for better understanding of the disk properties. The aim of the paper is to improve the knowledge of cluster parameters, using only the unprecedented quality of the Gaia photometry and astrometry. We have made use of the membership determination based on the precise Gaia astrometry and photometry. We applied an automated Bayesian tool, BASE-9, to fit stellar isochrones on the observed G, GBP, GRP magnitudes of the high probability member stars. We derive parameters such as age, distance modulus, and extinction for a sample of 269 open clusters, selecting only low reddening objects and discarding very young clusters, for which techniques other than isochrone-fitting are more suitable for estimating ages.
596. Ages and alpha-abundances of population in K2
ID:
ivo://CDS.VizieR/J/AJ/161/100
Title:
Ages and alpha-abundances of population in K2
Short Name:
J/AJ/161/100
Date:
19 Jan 2022 13:30:38
Publisher:
CDS
Description:
We explore the relationships between the chemistry, ages, and locations of stars in the Galaxy using asteroseismic data from the K2 mission and spectroscopic data from the Apache Point Galactic Evolution Experiment survey. Previous studies have used giant stars in the Kepler field to map the relationship between the chemical composition and the ages of stars at the solar circle. Consistent with prior work, we find that stars with high [{alpha}/Fe] have distinct, older ages in comparison to stars with low [{alpha}/Fe]. We provide age estimates for red giant branch (RGB) stars in the Kepler field, which support and build upon previous age estimates by taking into account the effect of {alpha}-enrichment on opacity. Including this effect for [{alpha}/Fe]-rich stars results in up to 10% older ages for low- mass stars relative to corrected solar mixture calculations. This is a significant effect that Galactic archeology studies should take into account. Looking beyond the Kepler field, we estimate ages for 735 RGB stars from the K2 mission, mapping age trends as a function of the line of sight. We find that the age distributions for low- and high-[{alpha}/Fe] stars converge with increasing distance from the Galactic plane, in agreement with suggestions from earlier work. We find that K2 stars with high [{alpha}/Fe] appear to be younger than their counterparts in the Kepler field, overlapping more significantly with a similarly aged low-[{alpha}/Fe] population. This observation may suggest that star formation or radial migration proceeds unevenly in the Galaxy.
597. Ages and [Fe/H] of M31 globular clusters
ID:
ivo://CDS.VizieR/J/A+A/549/A60
Title:
Ages and [Fe/H] of M31 globular clusters
Short Name:
J/A+A/549/A60
Date:
21 Oct 2021
Publisher:
CDS
Description:
The formation and evolution of disk galaxies are long standing questions in Astronomy. Understanding the properties of globular cluster systems can lead to important insights on the evolution of its host galaxy. We aim to obtain the stellar population parameters - age and metallicity - of a sample of M31 and Galactic globular clusters. Studying their globular cluster systems is an important step towards understanding their formation and evolution in a complete way.
598. Ages and masses for 920 LMC clusters
ID:
ivo://CDS.VizieR/J/ApJ/751/122
Title:
Ages and masses for 920 LMC clusters
Short Name:
J/ApJ/751/122
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present new age and mass estimates for 920 stellar clusters in the Large Magellanic Cloud (LMC) based on previously published broadband photometry and the stellar cluster analysis package, MASSCLEANage. Expressed in the generic fitting formula, d^2^N/dMdt{prop.to}M^{alpha}^t^{beta}^, the distribution of observed clusters is described by {alpha}=-1.5 to -1.6 and {beta}=-2.1 to -2.2. For 288 of these clusters, ages have recently been determined based on stellar photometric color-magnitude diagrams, allowing us to gauge the confidence of our ages. The results look very promising, opening up the possibility that this sample of 920 clusters, with reliable and consistent age, mass, and photometric measures, might be used to constrain important characteristics about the stellar cluster population in the LMC. We also investigate a traditional age determination method that uses a {chi}^2^ minimization routine to fit observed cluster colors to standard infinite-mass limit simple stellar population models. This reveals serious defects in the derived cluster age distribution using this method. The traditional {chi}^2^ minimization method, due to the variation of U, B, V, R colors, will always produce an overdensity of younger and older clusters, with an underdensity of clusters in the log(age/yr)=[7.0,7.5] range. Finally, we present a unique simulation aimed at illustrating and constraining the fading limit in observed cluster distributions that includes the complex effects of stochastic variations in the observed properties of stellar clusters.
599. Ages and masses of LMC clusters
ID:
ivo://CDS.VizieR/J/MNRAS/436/136
Title:
Ages and masses of LMC clusters
Short Name:
J/MNRAS/436/136
Date:
21 Oct 2021
Publisher:
CDS
Description:
Whether or not the rich star cluster population in the Large Magellanic Cloud (LMC) is affected by significant disruption during the first few x10^8^yr of its evolution is an open question and the subject of significant current debate. Here, we revisit the problem, adopting a homogeneous data set of broad-band imaging observations. We base our analysis mainly on two sets of self-consistently determined LMC cluster ages and masses, one using standard modelling and one which takes into account the effects of stochasticity in the clusters' stellar mass functions. On their own, the results based on any of the three complementary analysis approaches applied here are merely indicative of the physical conditions governing the cluster population. However, the combination of our results from all three different diagnostics leaves little room for any conclusion other than that the optically selected LMC star cluster population exhibits no compelling evidence of significant disruption - for clusters with masses, M_cl_, of log(M_cl_/M_{sun}_)>~3.0-3.5 - between the age ranges of [3-10 and 30-100]Myr, either 'infant mortality' or otherwise. In fact, there is no evidence of any destruction beyond that expected from simple models just including stellar dynamics and stellar evolution for ages up to 1Gyr. It seems, therefore, that the difference in environmental conditions in the Magellanic Clouds on the one hand and significantly more massive galaxies on the other may be the key to understanding the apparent variations in cluster disruption behaviour at early times.
600. Ages and masses of NGC1893 PMS stars
ID:
ivo://CDS.VizieR/J/other/NewA/19.1
Title:
Ages and masses of NGC1893 PMS stars
Short Name:
J/other/NewA/19.
Date:
21 Oct 2021
Publisher:
CDS
Description:
In this paper we continued our efforts to understand the star formation scenario in and around the young cluster NGC 1893. We used a sample of the young stellar sources (YSOs) identified on the basis of multiwavelength data (optical, near-infrared (NIR), mid-infrared (MIR) and X-ray) to study the nature of YSOs associated with the region. The identified YSOs show an age spread of ~5Myr. The YSOs located near the nebulae at the periphery of the cluster are relatively younger in comparison to those located within the cluster region. The present results are in accordance with those obtained by us in previous studies. Other main results from the present study are: 1) the fraction of disk bearing stars increases towards the periphery of the cluster; 2) there is an evidence supporting the notion that the mechanisms for disk dispersal operate less efficiently for low-mass stars; 3) the sample of Class II sources is found to be relatively older in comparison to that of Class III sources. A comparison of various properties of YSOs in the NGC 1893 region with those in the Tr 37/ IC 1396 region is also discussed.

Limit your search

more »

more »

more »

more »

more »

more »

more »

more »