arXiv 0911.07912009-11-04astro-ph.GAastro-ph.COastro-ph.SR

星团作为简单的恒星星族

Star clusters as simple stellar populations

A. Gustavo Bruzual

备注：: 17 pages, 6 figures. To appear as invited review article in a special issue of the Phil. Trans. Royal Soc. A: Ch. 5 "Star clusters as tracers of galactic star-formation histories" (ed. R. de Grijs). Fully peer reviewed. LaTeX, requires rspublic.cls style file

摘要：

在本文中，我回顾了我们在多大程度上可以理解星团的光度特性，以及低质量，未解决的星系，在人口合成模型，旨在描述“简单恒星星族”（SSP），即，在同一时间，在相同体积的空间中，从化学成分均匀的气体云中诞生的恒星群。由这些模型预测的光度特性不容易匹配的观测大多数星团，除非我们适当地考虑到预期的变化，在恒星的数量占据人口稀少的演化阶段，由于随机波动的恒星初始质量函数。在这种情况下，人口合成模型再现非常好的完整范围内观察到的综合颜色和绝对星等的星团的各种年龄和金属。星团颜色和星等的模型预测和观测之间的分歧可能表明建模中存在问题或缺陷，dioes并不一定告诉我们星团的行为不像SSP。用SSP模型匹配星团的光度特性是星团被认为是简单恒星星族的必要（但不是充分）条件。以复杂的恒星形成历史为特征的复合模型也与观测到的星团颜色相匹配。

英文摘要：

In this paper, I review to what extent we can understand the photometric properties of star clusters, and of low-mass, unresolved galaxies, in terms of population synthesis models designed to describe `simple stellar populations' (SSPs), i.e., groups of stars born at the same time, in the same volume of space, and from a gas cloud of homogeneous chemical composition. The photometric properties predicted by these models do not readily match the observations of most star clusters, unless we properly take into account the expected variation in the number of stars occupying sparsely populated evolutionary stages, due to stochastic fluctuations in the stellar initial mass function. In this case, population synthesis models reproduce remarkably well the full ranges of observed integrated colours and absolute magnitudes of star clusters of various ages and metallicities. The disagreement between the model predictions and observations of cluster colours and magnitudes may indicate problems with or deficiencies in the modelling, and dioes not necessarily tell us that star clusters do not behave like SSPs. Matching the photometric properties of star clusters using SSP models is a necessary (but not sufficient) condition for clusters to be considered simple stellar populations. Composite models, characterized by complex star-formation histories, also match the observed cluster colours.

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英文摘要：

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