AGES AND MASSES OF MILLION GALACTIC DISK MAIN SEQUENCE TURN-OFF AND SUB-GIANT STARS FROM THE LAMOST GALACTIC SPECTROSCOPIC SURVEYS
AGES AND MASSES OF MILLION GALACTIC DISK MAIN SEQUENCE TURN-OFF AND SUB-GIANT STARS FROM THE LAMOST GALACTIC SPECTROSCOPIC SURVEYS
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来自最新银河系光谱调查的百万颗银盘主序星和次巨星的年龄和质量
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发表时间：
2017
期刊：
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通讯作者：
Huo Z.Y.
中科院分区：
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作者：
Xiang M.S.;Liu X.W.;Shi J.R.;Yuan H.B.;Huo Z.Y.
e目前根据LAMOST银河系分光巡天估计了93万颗银河系盘主序星和次巨星的恒星年龄和质量。利用LAMOST光谱推断的有效温度Teff、绝对星等MV、金属丰度[Fe/H]和α元素/铁丰度比[α/Fe]，通过贝叶斯算法与恒星等时线匹配，确定了年龄和质量。广泛的检查表明年龄和质量估计是可靠的。整个样本星的年龄估计的中位误差为34%，年龄大于2 Gyr的恒星中有一半的年龄不确定性仅为20%-30%，整个样本星的质量估计的中位误差为1.8%。特别地，在年龄-[α/Fe]和年龄-[Fe/H]（[α/H]）空间中均显示出双序列特征。在[Fe/H]-[α/Fe]空间中，8- 10 Gyr的恒星同时具有薄盘序列和厚盘序列，而年轻（年老）的恒星仅具有薄盘序列，表明薄盘在8- 10 Gyr前变得突出，而厚盘在8 Gyr前形成较早且几乎淬灭。恒星年龄在星盘上呈现正的垂直梯度和负的径向梯度，在R9 kpc的外盘上呈现出强烈的耀斑。
e present estimates of stellar age and mass for 0.93 million Galactic disk main sequence turn-off and sub-giant stars from the LAMOST Galactic Spectroscopic Surveys. The ages and masses are determined by matching with stellar isochrones using Bayesian algorithm, utilizing effective temperature Teff, absolute magnitude MV , metallicity [Fe/H] and α-element to iron abundance ratio [α/Fe] deduced from the LAMOST spectra. Extensive examinations suggest the age and mass estimates are robust. The overall sample stars have a median error of 34 per cent for the age estimates, and half of the stars older than 2 Gyr have age uncertainties of only 20–30 per cent. Median error for the mass estimates of the whole sample stars is ∼ 8 per cent. The huge dataset demonstrates good correlations among stellar age, [Fe/H] ([α/H]) and [α/Fe]. Particularly, double sequence features are revealed in the both the age–[α/Fe] and age–[Fe/H]([α/H]) spaces. In the [Fe/H]–[α/Fe] space, stars of 8–10Gyr exhibit both the thin and thick disk sequences, while younger (older) stars show only the thin (thick) disk sequence, indicating that the thin disk became prominent 8–10Gyr ago, while the thick disk formed earlier and almost quenched 8Gyr ago. Stellar ages exhibit positive vertical and negative radial gradients across the disk, and the outer disk of R 9 kpc exhibits a strong flare in stellar age distribution.