NONLINEAR COLOR–METALLICITY RELATIONS OF GLOBULAR CLUSTERS. III. ON THE DISCREPANCY IN METALLICITY BETWEEN GLOBULAR CLUSTER SYSTEMS AND THEIR PARENT ELLIPTICAL GALAXIES
NONLINEAR COLOR–METALLICITY RELATIONS OF GLOBULAR CLUSTERS. III. ON THE DISCREPANCY IN METALLICITY BETWEEN GLOBULAR CLUSTER SYSTEMS AND THEIR PARENT ELLIPTICAL GALAXIES
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DOI：
10.1088/0004-637x/743/2/150
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发表时间：
2011-09
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通讯作者：
Suk-Jin Yoon;Sang-Yoon Lee;J. Blakeslee;E. Peng;S. Sohn;Jaeil Cho;Hak-Sub Kim;C. Chung;Sooyoung Kim;Young-Wook Lee
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作者：
Suk-Jin Yoon;Sang-Yoon Lee;J. Blakeslee;E. Peng;S. Sohn;Jaeil Cho;Hak-Sub Kim;C. Chung;Sooyoung Kim;Young-Wook Lee
河外天文学的难题之一是观测到的早期型星系的两个主要组成部分-球状星团（GC）和晕场星之间的金属丰度分布函数（MDF）的差异。这通常被认为是GC系统和它们的母星系之间高度分离的演化历史的证据。然而，在这里，我们表明，在连接所观察到的GC颜色，其内在的金属性的新的发展建议非线性的颜色到金属性的转换，这将观察到的颜色分布转化为强烈的峰值，单峰的MDF与广泛的贫金属的尾巴。值得注意的是，推断的GC MDFs是类似的解析场星附近的椭圆星系的MDFs和化学演化模型的星系。气相色谱仪的形状，其特征是一个尖锐的峰与金属贫尾部，表明一个几乎连续的化学富集与一个相对较短的时间尺度。特征形状出现在宿主星系质量的三个数量级上，表明各种GC系统之间存在普遍的化学富集过程。由于GC比同一星系中的场星更蓝，因此GC的化学富集过程比场星的化学富集过程稍早停止是合理的，如果是这样的话，GC优先跟踪星系形成中主要的、充满活力的星星形成事件。我们进一步提出了GC系统之间可能存在的系统性年龄差异，即在更明亮的星系中GC系统更老。这是一致的缩小范式，即恒星的明亮的星系，平均而言，形成早于那些较暗的星系;这也支持了类似的性质所共享的GC和场星。尽管本研究中使用的样本（哈勃太空望远镜高级巡天相机/宽场通道，WFPC 2和WFC 3测光的GC系统在室女座星系团）限制我们的讨论R Re的巨大椭圆和10 Re的正常椭圆，我们的研究结果表明，GC系统和他们的母星系有一个更共同的起源比以前认为的，从而大大简化了星系形成的理论。
One of the conundrums in extragalactic astronomy is the discrepancy in observed metallicity distribution functions (MDFs) between the two prime stellar components of early-type galaxies—globular clusters (GCs) and halo field stars. This is generally taken as evidence of highly decoupled evolutionary histories between GC systems and their parent galaxies. Here we show, however, that new developments in linking the observed GC colors to their intrinsic metallicities suggest nonlinear color-to-metallicity conversions, which translate observed color distributions into strongly peaked, unimodal MDFs with broad metal-poor tails. Remarkably, the inferred GC MDFs are similar to the MDFs of resolved field stars in nearby elliptical galaxies and those produced by chemical evolution models of galaxies. The GC MDF shape, characterized by a sharp peak with a metal-poor tail, indicates a virtually continuous chemical enrichment with a relatively short timescale. The characteristic shape emerges across three orders of magnitude in the host galaxy mass, suggesting a universal process of chemical enrichment among various GC systems. Given that GCs are bluer than field stars within the same galaxy, it is plausible that the chemical enrichment processes of GCs ceased somewhat earlier than that of the field stellar population, and if so, GCs preferentially trace the major, vigorous mode of star formation events in galactic formation. We further suggest a possible systematic age difference among GC systems, in that the GC systems in more luminous galaxies are older. This is consistent with the downsizing paradigm whereby stars of brighter galaxies, on average, formed earlier than those of dimmer galaxies; this additionally supports the similar nature shared by GCs and field stars. Although the sample used in this study (the Hubble Space Telescope Advanced Camera for Surveys/Wide Field Channel, WFPC2, and WFC3 photometry for the GC systems in the Virgo galaxy cluster) confines our discussion to R ≲ Re for giant ellipticals and ≲10 Re for normal ellipticals, our findings suggest that GC systems and their parent galaxies have shared a more common origin than previously thought, and hence greatly simplify theories of galaxy formation.