Evolution of Globular Clusters Formed in Mergers
Evolution of Globular Clusters Formed in Mergers
复制标题
合并中形成的球状星团的演化
DOI：
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发表时间：
2001
期刊：
影响因子：
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通讯作者：
R. Larson
中科院分区：
文献类型：
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作者：
L. Martinet;R. Larson
在星系合并中形成的球状星团（例如，An-tennae）现在可以在它们演化的不同阶段进行研究。在年轻的合并残留物中（例如，NGC 7252），这些“第二代”球状星团以数百个年轻的光晕团的形式出现，其金属含量与太阳大致相同。虽然一开始比古老的缺乏金属的球状星团更蓝、更亮，但它们在1 - 1.5 Gyr之后变得更红，然后可以在看起来扰动的E和50星系（例如NGC 1316、1700和3610）中观察到仍然是中等年龄的超亮红色星团。从颜色分布、投射的径向分布，或许还有光度函数来看，这些星团最终具有在许多巨大椭圆中观察到的富含红色金属的球状星团的特性。对正在进行的合并中的球状星团和年轻残余物的研究表明，第二代球状星团形成于巨大的分子云，受到合并引起的星爆中快速增加的压力的冲击。这种压力诱导的形成为Cen（2001）的论点提供了证据，即在z≈7 - 15的宇宙学再电离过程中，一般压力的增加触发了在所有类型的星系中观测到的第一代低金属球状星团的几乎同时形成。
Globular clusters formed in galactic mergers (e.g., The An-tennae) can now be studied at different stages of their evolution. In young merger remnants (e.g., NGC 7252) these " second-generation " globulars appear by the hundreds as young halo clusters of roughly solar metallic-ity. While at first bluer and much more luminous than old metal-poor globulars, they become redder after 1 – 1.5 Gyr and can then be observed as still overluminous red clusters of intermediate age in perturbed-looking E and S0 galaxies (e.g., NGC 1316, 1700, 3610). There is evidence from the color distributions, projected radial distributions, and perhaps also luminosity functions that these clusters eventually assume the properties of red metal-rich globulars observed in many giant ellipticals. Studies of globular clusters in ongoing mergers and young remnants suggest that second-generation globulars form from giant molecular clouds shocked by the rapid pressure increase in the merger-induced starburst. This pressure-induced formation lends credence to Cen's (2001) argument that the general pressure increase during cosmological reionization at z ≈ 7 – 15 triggered the near-simultaneous formation of the universal population of first-generation metal-poor globulars observed in galaxies of all types.