Ages of Main-sequence Turnoff Stars from the GALAH Survey

Chen, Xunzhou; Ge, Zhishuai; Chen, Yuqin; Bi, Shaolan; Jiang, Yu; Yang, Wuming; Ferguson, Jason W.; Wu, Yaqian; Li, Yaguang

doi:10.3847/1538-4357/ac55a1

Cited by 4 publications

(3 citation statements)

References 51 publications

(53 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Notably, at fixed [Fe/H], the abundance variations of individual elements exert a consequential impact on the overall metallicity Z, which subsequently determines the opacity of the stellar models. This, in turn, influences the efficiency of energy transfer and the thermal structure, thereby altering the evolution tracks on the H-R diagram and the main-sequence (MS) lifetime (e.g., VandenBerg et al 2012;Chen et al 2022). Consequently, in the context of stellar modeling, it is essential to consider the proper metal mixture in order to accurately characterize stars and determine their ages.…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, Ge et al (2016) proposed the COextreme models, which treat oxygen abundance differently from the other α elements and add carbon abundance in the stellar evolution models. The models have been employed to determine the ages of thousands of metal-poor halo stars, disk stars, and MS turn-off stars (Ge et al 2016;Chen et al 2020Chen et al , 2022. These results showed that increasing oxygen abundance leads to smaller age determination for the stars with [Fe/H] < −0.2.…”

Section: Introductionmentioning

confidence: 99%

“…For the stars with [Fe/H] < −0.2 and [O/α] > 0.2 dex, the age difference would be about 1 Gyr. Due to the limited sample sizes of previous studies (Ge et al 2016, with 70 stars, andChen et al 2020, with 148 stars) or the restricted range of [Fe/H] values ([Fe/H]  −0.1 dex; Chen et al 2022), there is a pressing need for a large and selfconsistent sample to conduct a quantitative analysis regarding the impact of O enhancement on age determination.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Age of FGK Dwarfs Observed with LAMOST and GALAH: Considering the Oxygen Enhancement

Sun,

Ge,

Chen

et al. 2023

ApJS

Self Cite

View full text Add to dashboard Cite

Varying oxygen abundance could impact modeling-inferred ages. This work aims to estimate the ages of dwarfs considering observed oxygen abundance. To characterize 67,503 LAMOST and 4006 GALAH FGK-type dwarf stars, we construct a grid of stellar models, which take into account oxygen abundance as an independent model input. Compared with ages determined with commonly used α-enhanced models, we find a difference of ∼9% on average when the observed oxygen abundance is considered. The age differences between the two types of models are correlated to [Fe/H] and [O/α], and they are relatively significant on stars with [Fe/H] ≲ −0.6 dex. Generally, varying 0.2 dex in [O/α] will alter the age estimates of metal-rich (−0.2 < [Fe/H] < 0.2) stars by ∼10% and relatively metal-poor (−1 < [Fe/H] < −0.2) stars by ∼15%. Of the low-O stars with [Fe/H] < 0.1 dex and [O/α] ∼−0.2 dex, many have fractional age differences of ≥ 10% and even reach up to 27%. The fractional age difference of high-O stars with [O/α] ∼0.4 dex reaches up to −33% to −42% at [Fe/H] ≲ −0.6 dex. We also analyze the chemical properties of these stars. We find a decreasing trend of [Fe/H] with ages from 7.5–9 Gyr to 5–6.5 Gyr for the stars from the LAMOST and GALAH. The [O/Fe] of these stars increases with decreasing age from 7.5–9 Gyr to 3–4 Gyr, indicating that the younger population is more O rich.

show abstract

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Age of FGK Dwarfs Observed with LAMOST and GALAH: Considering the Oxygen Enhancement

Sun,

Ge,

Chen

et al. 2023

ApJS

Self Cite

View full text Add to dashboard Cite

show abstract

$\mathrm{H}{\alpha }$ chromospheric activity of F-, G-, and K-type stars observed by the LAMOST medium-resolution spectroscopic survey

Zhang

et al. 2023

Astrophys Space Sci

View full text Add to dashboard Cite

The role of radial migration in open cluster and field star populations withGaiaDR3

Viscasillas Vázquez,

Magrini,

Spina

et al. 2023

A&A

View full text Add to dashboard Cite

Context. The survival time of a star cluster depends on its total mass, density, and thus size, as well as on the environment in which it was born and in which lies. Its dynamical evolution is influenced by various factors such as gravitational effects of the Galactic bar, spiral structures, and molecular clouds. Overall, the factors that determine the longevity of a cluster are complex and not fully understood. Aims. This study aims to investigate whether open clusters and field stars respond differently to the perturbations that cause radial migration. In particular, we aim to understand the nature of the oldest surviving clusters. Methods. We compared the time evolution of the kinematic properties of two Gaia DR3 samples. The first sample is composed of ∼40 open clusters and the second one of ∼66 000 main sequence turn off field stars. Both of the samples are composed of stars selected with the same quality criterion, and they belong to the thin disc, are in a similar metallicity range, are located in the same Galactocentric region [7.5–9 kpc], and have ages greater than 1 Gyr. We performed a statistical analysis comparing the properties of the samples of the field stars and of the open clusters. Results. A qualitative comparison of kinematic and orbital properties revealed that clusters younger than 2–3 Gyr are more resistant to perturbations than field stars, and they move along quasi-circular orbits. Conversely, clusters older than approximately 3 Gyr have more eccentric and inclined orbits than isolated stars in the same age range. Such orbits lead the older clusters to reach higher elevations on the Galactic plane, maximising their probability to survive several more gigayears. A formal statistical analysis revealed that there are differences among the time evolution of most of the kinematic and orbital properties of the field stars and open clusters. However, the comparison between some properties (e.g., Vϕ and LZ) do not reach a sufficient statistical significance. Conclusions. Our results suggest that the oldest surviving clusters are usually more massive and move on orbits with a higher eccentricity. Although they are still reliable tracers of the Galaxy’s past composition, they do not reflect the composition of the place where they are currently found. Therefore, we cannot avoid considering kinematic properties when comparing data and models of chemical evolution and also taking into account the intrinsic differences between clusters and isolated stars. To validate the results, new studies that increase the sample of open clusters, especially at older ages, are needed.

show abstract

Ages of Main-sequence Turnoff Stars from the GALAH Survey

Cited by 4 publications

References 51 publications

Age of FGK Dwarfs Observed with LAMOST and GALAH: Considering the Oxygen Enhancement

Age of FGK Dwarfs Observed with LAMOST and GALAH: Considering the Oxygen Enhancement

$\mathrm{H}{\alpha }$ chromospheric activity of F-, G-, and K-type stars observed by the LAMOST medium-resolution spectroscopic survey

The role of radial migration in open cluster and field star populations withGaiaDR3

Contact Info

Product

Resources

About