Keck Spectroscopy of Globular Clusters in the Virgo Cluster Dwarf Elliptical Galaxy VCC 1386
Keck Spectroscopy of Globular Clusters in the Virgo Cluster Dwarf Elliptical Galaxy VCC 1386
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处女座星团矮椭圆星系 VCC 1386 球状星团的凯克光谱
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发表时间：
2005
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影响因子：
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通讯作者：
C. Conselice
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作者：
C. Conselice
我们提出了一个Keck光谱研究的球状星团与室女座星系团矮椭圆星系（dE）VCC 1386的结果。我们分析了蓝色光谱吸收线从3500到5500的13个球状星团候选人，并确认五个与VCC 1386。通过比较这些球状星团的金属和巴耳末线指数与α增强的单星星族模型，我们发现这些系统是贫金属的，[Fe/H] >-1.35，并且年龄大，在3 σ置信度下年龄>5 Gyr，将它们的形成置于z = 1。这是第一个光谱研究的球状星团周围的dEs在一个集群，揭示了一些低质量的星系在丰富的环境中形成至少部分的恒星质量在宇宙的历史早期。我们进一步发现，VCC 1386本身的光度加权恒星人口比它的球状星团更年轻，更富含金属，与哈勃太空望远镜成像的（V-I）0颜色一致。这意味着VCC 1386和本星系团dEs一样，有多个星星形成的插曲。然而，与低光度系统相关的球状星团似乎与巨星系相关的球状星团一样古老，这与它们的主体恒星群的“缩小”形成相反。
We present the results of a Keck spectroscopic study of globular clusters associated with the Virgo Cluster dwarf elliptical galaxy (dE) VCC 1386. We analyze blue spectroscopic absorption lines from 3500 to 5500 Å for 13 globular cluster candidates and confirm that five are associated with VCC 1386. By comparing metal and Balmer line indices of these globular clusters with α-enhanced single stellar population models, we find that these systems are metal poor, with [Fe/H] > -1.35, and old, with ages >5 Gyr at 3 σ confidence, placing their formation at z ≳ 1. This is one of the first spectroscopic studies of globular clusters surrounding dEs in a cluster, revealing that some low-mass galaxies in rich environments form at least part of their stellar mass early in the history of the universe. We further find that the luminosity-weighted stellar population of VCC 1386 itself is younger and more metal rich than its globular clusters, consistent with (V - I)0 colors from Hubble Space Telescope imaging. This implies that VCC 1386, like the Local Group dEs, has had multiple episodes of star formation. Globular clusters associated with low-luminosity systems, however, appear to be roughly as old as those associated with giant galaxies, contrary to the "downsizing" formation of their bulk stellar populations.