The Birth of Star Clusters
The Birth of Star Clusters
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DOI：
10.1007/978-3-319-22801-3
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发表时间：
2018
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影响因子：
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通讯作者：
S. Stahler
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作者：
S. Stahler
长期以来，人们一直认为大多数恒星都是群体而不是孤立的。这些群体本身是如何产生的，这是一个重大的未解之谜。乍一看，这样的问题存在似乎很奇怪。当然，我们当然不了解单个恒星如何形成的每一个细节。对于快速驱散任何母气的大质量恒星，我们的无知尤其严重。然而，对于像太阳这样更常见的低质量恒星，一个大致的图像已经存在了一段时间，并继续被填充。那么，为什么还有一个单独的集群形成问题呢？如果我们向前跳几十年，想象低质量恒星的诞生更加安全，这样的问题还会存在吗？答案是肯定的，至少有两个基本原因。首先，有一个明显的事实，恒星群是由更大的分子云形成的，而不是由密集的核心产生的单个太阳型物体。这些实体相对静止，主要由普通的热压力支撑，这一事实有助于理解致密核的结构和动力学。相比之下，所有质量足以形成星团的云都以内部湍流为特征，定量建模充其量仍然是原始的。这个难题将持续存在的第二个原因是恒星群跨越了巨大的性质范围。有由几十名成员组成的移动团体。在光谱的另一端是巨大而古老的球状星团，其中一些仍然包含一百万颗恒星。正如没有一个单星形成的理论模型可能同时解释M矮星和O星一样，同样令人难以置信的是，一种机制是如此不同的恒星聚集体的基础。目前，我们必须考虑问题的不同方面，并尽最大努力了解这些方面。在本卷中，我们提供了一个选择目前的研究，从观察家和理论家，在这个活跃的研究领域的关键议题。我们开始的帐户非常年轻的集群，那些仍然嵌入在相对较大的和动荡的分子云。Joana Ascenso首先告诉我们如何在实践中识别这些群体。考虑到光学显示的簇的多样性，它们的光学显示对应物表现出一系列的形态也就不足为奇了，Ascenso也描述了这些形态。到目前为止，我们还没有办法确定这些群体的大致年龄。我们也还不能确定的具体先行者，v
It has long been accepted that most stars originate in groups, rather than in isolation. How the groups themselves arise is a major, unsolved puzzle. At first sight, it might seem odd that such a problem should exist at all. Granted, we certainly do not understand every detail of how individual stars form. Our ignorance is especially severe in the case of massive stars that quickly disperse any parent gas. For the more common, lower-mass stars like the Sun, however, a general picture has been in place for some time, and continues to be filled in. Why, then, is there a separate problem of cluster formation? If we jump ahead a few decades and imagine that low-mass stellar birth is even more secure, will such a problem remain? The answer is that it would, for at least two basic reasons. First, there is the obvious fact that stellar groups form out of much larger molecular clouds than the dense cores spawning single, solar-type objects. Understanding the structure and dynamics of dense cores is facilitated by the fact that these entities are relatively quiescent, supported largely by ordinary thermal pressure. In contrast, all clouds massive enough to form clusters are characterized by internal turbulence, for which quantitative modeling remains primitive at best. A second reason the conundrum will persist is that stellar groups span an enormous range of properties. There are moving groups consisting of a few dozen members. At the opposite end of the spectrum are the monstrous and ancient globular clusters, some of which still contain a million stars. Just as no one theoretical model of single-star formation is likely to explain both M dwarfs and O stars, it is equally implausible that one mechanism underlies such diverse stellar aggregates. We must, at present, consider different aspects of the problem and do our best to understand them. In this volume, we offer a selection of current research, from both observers and theorists, on key topics in this active field of study. We begin with an account of the very youngest clusters, those still embedded in relatively large and turbulent molecular clouds. Joana Ascenso first tells us how these groups are identified in practice. Given the variety of optically revealed clusters, it is not surprising that their optically revealed counterparts exhibit a range of morphologies, which Ascenso also describes. As yet, we have no means to assign even rough ages to these groups. Nor can we yet identify the specific forerunners of, v