Central energy equipartition in multimass models of globular clusters
Central energy equipartition in multimass models of globular clusters
复制标题
球状星团多质量模型中的中心能量均分
DOI：
10.1111/j.1365-2966.2005.09842.x
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发表时间：
2005
影响因子：
4.8
通讯作者：
P. Miocchi
中科院分区：
文献类型：
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作者：
P. Miocchi
在球状星团多质量King-Michie模型的构造中，不同质量恒星之间的近似中心能量均分通常是通过将每个质量级的速度参数与恒星质量成反比来实现的，就好像分布函数是等温的。在本文中，这种“等温近似”已被检查，其后果的模型参数研究的比较模型，包括中心能量均分正确。据发现，等温近似下，一对组件的“温度”可以不同的低浓度分布的一个不可忽略的量。它还发现，在一般情况下，这种近似导致一个显着减少的质量偏析相比，根据在中心的确切能量均分。作为一个代表性的例子，各向同性三分量模型拟合一个给定的投影表面亮度和视线速度色散分布进行了讨论。在这个例子中，等温近似给出了一个比真实均分（W = 5.9 x 10 - 2）更集中的簇包络（中心无量纲势W = 3.3），以及更高的质量函数对数斜率。因此，推断的总质量（以及全球质光比）比正确值低1.4倍，而重暗遗迹的质量则小3.3倍。在能量均分的情况下，质量低于一定极限的恒星的命运是逃离系统。这个极限是作为一个函数的质量和W的组成部分的巨星和关闭的恒星。
In the construction of multimass King-Michie models of globular clusters, an approximated central energy equipartition between stars of different mass is usually imposed by scaling the velocity parameter of each mass class inversely with the stellar mass, as if the distribution function were isothermal. In this paper, this 'isothermal approximation' has been checked and its consequences on the model parameters studied by a comparison with models including central energy equipartition correctly. It is found that, under the isothermal approximation, the 'temperatures' of a pair of components can differ to a non-negligible amount for low concentration distributions. It is also found that, in general, this approximation leads to a significantly reduced mass segregation in comparison with that given under the exact energy equipartition at the centre. As a representative example, an isotropic three-component model fitting a given projected surface brightness and line-of-sight velocity dispersion profiles is discussed. In this example, the isothermal approximation gives a cluster envelope much more concentrated (central dimensionless potential W = 3.3) than under the true equipartition (W = 5.9 x 10 -2 ), as well as a higher mass function logarithmic slope. As a consequence, the inferred total mass (and then the global mass-to-light ratio) is a factor of 1.4 times lower than the correct value and the amount of mass in heavy dark remnants is 3.3 times smaller. Under energy equipartition, the fate of stars having a mass below a certain limit is to escape from the system. This limit is derived as a function of the mass and W of the component of giant and turn-off stars.