THE GLOBULAR CLUSTER SYSTEM OF NGC 4636 AND FORMATION OF GLOBULAR CLUSTERS IN GIANT ELLIPTICAL GALAXIES
THE GLOBULAR CLUSTER SYSTEM OF NGC 4636 AND FORMATION OF GLOBULAR CLUSTERS IN GIANT ELLIPTICAL GALAXIES
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DOI：
10.1088/0004-637x/759/2/116
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发表时间：
2012-09
期刊：
影响因子：
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通讯作者：
H. S. Park;M. Lee;H. Hwang;Sang Chul Kim;N. Arimoto;Y. Yamada;N. Tamura;M. Onodera
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文献类型：
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作者：
H. S. Park;M. Lee;H. Hwang;Sang Chul Kim;N. Arimoto;Y. Yamada;N. Tamura;M. Onodera
本文对室女座星系团中的巨型椭圆星系NGC 4636中的球状星团进行了金属丰度、年龄和α元素的光谱分析。用斯巴鲁8.2米望远镜上的暗天体照相机和摄谱仪获得的积分光谱测量了GC的线指数。利用Brodie & Huchra方法计算了59个GC的[Fe/H]值，并将Lick线指数与单星族模型进行了比较，得到了33个GC的[Z/H]、年龄和[α/Fe]值。NGC 4636 GC的金属丰度分布显示出双峰性，在[Fe/H] = -1.23（σ = 0.32）和−0.35（σ = 0.19）处有两个峰值。年龄分布很大，从2岁到15岁，年轻GC的比例为99.9%。所有这些创业公司都有一些年龄小于5岁的年轻创业公司。富金属GC（[Fe/H] >-0.9）的平均年龄比贫金属GC年轻约3 Gyr。gE GC的[α/Fe]平均值小于银河系GC。我们讨论了这些结果的背景下，GC形成的GE。
We present a spectroscopic analysis of the metallicities, ages, and alpha-elements of the globular clusters (GCs) in the giant elliptical galaxy (gE) NGC 4636 in the Virgo Cluster. Line indices of the GCs are measured from the integrated spectra obtained with Faint Object Camera and Spectrograph on the Subaru 8.2 m Telescope. We derive [Fe/H] values of 59 GCs based on the Brodie & Huchra method, and [Z/H], age, and [α/Fe] values of 33 GCs from the comparison of the Lick line indices with single stellar population models. The metallicity distribution of NGC 4636 GCs shows a hint of a bimodality with two peaks at [Fe/H] = -1.23(σ = 0.32) and −0.35(σ = 0.19). The age spread is large from 2 Gyr to 15 Gyr and the fraction of young GCs with age 99.9%. All these gEs harbor some young GCs with ages less than 5 Gyr. The mean age of the metal-rich GCs ([Fe/H] >−0.9) is about 3 Gyr younger than that of the metal-poor GCs. The mean value of [α/Fe] of the gE GCs is smaller than that of the Milky Way GCs. We discuss these results in the context of GC formation in gEs.