The state of globular clusters at birth: emergence from the gas-embedded phase
The state of globular clusters at birth: emergence from the gas-embedded phase
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DOI：
10.1093/mnras/stt1825
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发表时间：
2013-09
影响因子：
4.8
通讯作者：
N. Leigh;M. Giersz;J. Webb;A. Hypki;G. Marchi;P. Kroupa;A. Sills
中科院分区：
文献类型：
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作者：
N. Leigh;M. Giersz;J. Webb;A. Hypki;G. Marchi;P. Kroupa;A. Sills
本文讨论了De Marchi，Presce和Pulone所报道的星团浓度c与现今质量函数斜率α之间的关联的来源。这个关系既可以从普遍的初始条件结合一些动力学机制(S)重现，这些动力机制改变(S)随时间变化的星团结构和质量函数，或者它必须出现在星团寿命的早期，例如在星团形成的气体嵌入阶段。分别用MOCCA和NBODY6程序进行球状星团演化的蒙特卡罗模型和N体模型的组合，我们探索了一些可能影响观测关系的动力学机制。在所考虑的初始条件范围内，我们的结果与普适的初始二元分数�为10%(然而，这并不排除100%)和普适的初始恒星质量函数类似于标准的Kroupa分布是一致的。在c-α关系中观察到的大部分色散可以归因于双体弛豫和银河系潮汐。然而，仅靠动力过程不可能再现浓度上的色散，我们需要至少在初始浓度和总星团质量之间有一定的关联。我们认为，这一趋势的起源可能与星系团演化的气体嵌入阶段有关。
In this paper, we discuss the origin of the observed correlation between cluster concentration c and present-day mass function (PDMF) slope α reported by De Marchi, Paresce & Pulone. This relation can either be reproduced from universal initial conditions combined with some dynamical mechanism(s) that alter(s) the cluster structure and mass function over time, or it must arise early on in the cluster lifetime, such as during the gas-embedded phase of cluster formation. Using a combination of Monte Carlo and N-body models for globular cluster evolution performed with the MOCCA and NBODY6 codes, respectively, we explore a number of dynamical mechanisms that could affect the observed relation. For the range of initial conditions considered here, our results are consistent with an universal initial binary fraction � 10% (which does not, however, preclude 100%) and an universal initial stellar mass function resembling the standard Kroupa distribution. Most of the dispersion observed in the c-α relation can be attributed to twobody relaxation and Galactic tides. However, dynamical processes alone could not have reproduced the dispersion in concentration, and we require at least some correlation between the initial concentration and the total cluster mass. We argue that the origin of this trend could be connected to the gas-embedded phase of cluster evolution.