THE LAMOST SPECTROSCOPIC SURVEY OF STAR CLUSTERS IN M31. II. METALLICITIES, AGES, AND MASSES
THE LAMOST SPECTROSCOPIC SURVEY OF STAR CLUSTERS IN M31. II. METALLICITIES, AGES, AND MASSES
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DOI：
10.3847/0004-6256/152/2/45
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发表时间：
2016-05
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通讯作者：
Bing-Gan Chen;Xiaowei Liu;M. Xiang;Hailong Yuan;Y. Huang;Jian-rong Shi;Z. Fan;Z. Huo;Chun Wang;Juanjuan Ren;Z. Tian;Hua-Wei Zhang;Gaochao Liu;Z. Cao;Yong Zhang;Yong-Hui Hou;Yuefei Wang
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作者：
Bing-Gan Chen;Xiaowei Liu;M. Xiang;Hailong Yuan;Y. Huang;Jian-rong Shi;Z. Fan;Z. Huo;Chun Wang;Juanjuan Ren;Z. Tian;Hua-Wei Zhang;Gaochao Liu;Z. Cao;Yong Zhang;Yong-Hui Hou;Yuefei Wang
本文选取了大天区多目标光纤光谱望远镜（LAMOST）在M31和M33近区观测到的306个大质量星星团的样品，测定了它们的金属丰度、年龄和质量。金属丰度和年龄是通过使用像素到像素的光谱拟合技术将观测到的积分光谱与恒星合成种群（SSP）模型进行拟合来估计的。大多数年轻星系团的年龄也是通过拟合模型光谱能量分布（SED）的多波段光度测量。星系团的估计年龄跨度很大，从几百万年到宇宙的年龄。年龄小于和大于1 Gyr的集群数量分别为46和260。与年龄和金属丰度的确定，集群质量，然后估计通过比较多波段光度测量与SSP模型SED。导出的质量范围从到M，峰值为和M的年轻（Gyr）和老（Gyr）集群，分别。我们估计的金属丰度、年龄和质量与现有文献值吻合得很好。比[Fe/H] dex-0.7更丰富的古老星团有着广泛的年龄范围。那些比[Fe/H] δ-0.7 dex更差的星团似乎由两组组成，就像以前在银河系球状星团中发现的那样--其中一组年龄最老，所有金属丰度值都低于dex，另一组金属丰度值随着年龄的减小而增加。M 31内盘（0-30 kpc）的老星系团显示出明显的金属丰度梯度，测量值为-0.038 ± 0.023 dex kpc−1。
We select from Paper I a sample of 306 massive star clusters observed with the Large Sky Area Multi–Object Fibre Spectroscopic Telescope (LAMOST) in the vicinity fields of M31 and M33, and determine their metallicities, ages, and masses. Metallicities and ages are estimated by fitting the observed integrated spectra with stellar synthesis population (SSP) models with a pixel–to–pixel spectral fitting technique. Ages for most young clusters are also derived by fitting the multi–band photometric measurements with model spectral energy distributions (SEDs). The estimated cluster ages span a wide range, from several million years to the age of the universe. The numbers of clusters younger and older than 1 Gyr are, respectively, 46 and 260. With ages and metallicities determined, cluster masses are then estimated by comparing the multi–band photometric measurements with SSP model SEDs. The derived masses range from to M⊙, peaking at and M⊙ for young ( Gyr) and old ( Gyr) clusters, respectively. Our estimated metallicities, ages, and masses are in good agreement with available literature values. Old clusters richer than [Fe/H] ∼ −0.7 dex have a wide range of ages. Those poorer than [Fe/H] ∼ −0.7 dex seem to be composed of two groups, as previously found for Galactic globular clusters—one of the oldest ages with all values of metallicity down to dex and another with metallicity increasing with decreasing age. The old clusters in the inner disk of M 31 (0–30 kpc) show a clear metallicity gradient measured at −0.038 ± 0.023 dex kpc−1.