NEW TESTS FOR DISRUPTION MECHANISMS OF STAR CLUSTERS: THE LARGE AND SMALL MAGELLANIC CLOUDS
NEW TESTS FOR DISRUPTION MECHANISMS OF STAR CLUSTERS: THE LARGE AND SMALL MAGELLANIC CLOUDS
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DOI：
10.1088/0004-637x/711/2/1263
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发表时间：
2010-02
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影响因子：
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通讯作者：
R. Chandar;S. M. Fall;B. Whitmore
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作者：
R. Chandar;S. M. Fall;B. Whitmore
我们将观测到的大麦哲伦星云（LMC）中星团的质量(M)和年龄（τ）的二元分布与三种星团破裂的理想模型的预测分布g（M, τ）进行了比较：(1)突然的质量依赖破裂，(2)逐渐的质量依赖破裂，(3)逐渐的质量无关破裂。具有质量无关破坏的模型提供了这些星团总体的良好的一阶描述，其中g(M, τ)∝Mβτγ, β = - 1.8±0.2和γ = - 0.8±0.2，至少对于年龄τ > 109 yr和质量M > 103M☉(更具体地说，τ > 107（M/102M☉）1.3 yr的星团来说是这样。该模型预测星团应该具有幂律光度函数dN/dL∝L−1.8，与观测结果一致。另一方面，前两个模型在描述观测结果时表现不佳，反驳了先前的说法，即在研究的M -τ域中，在LMC中观察到星团的质量依赖破坏。SMC中的簇可以用与LMC相同的g（M, τ）分布来描述，但样本更小，因此不确定性更大。麦哲伦星云中星系团的成功的g（M, τ）模型实际上与天线星系合并中的星系团相同，但将有效性领域扩展到低质量和更老的年龄。这表明在这些非常不同的星系中，主要的破坏过程至少在τ > 108年，可能在τ > 109年是相似的。LMC中年轻星团的质量函数是幂律，而古老的球状星团的质量函数是峰值。我们表明，观察到的这些质量函数的形状与McLaughlin和Fall提出的简单蒸发模型的预期一致。
We compare the observed bivariate distribution of masses (M) and ages (τ) of star clusters in the Large Magellanic Cloud (LMC) with the predicted distributions g(M, τ) from three idealized models for the disruption of star clusters: (1) sudden mass-dependent disruption, (2) gradual mass-dependent disruption, and (3) gradual mass-independent disruption. The model with mass-independent disruption provides a good, first-order description of these cluster populations, with g(M, τ) ∝ Mβτγ, β = −1.8 ± 0.2 and γ = −0.8 ± 0.2, at least for clusters with ages τ ≲ 109 yr and masses M ≳ 103M☉ (more specifically, τ ≲ 107(M/102M☉)1.3 yr). This model predicts that the clusters should have a power-law luminosity function, dN/dL ∝ L−1.8, in agreement with observations. The first two models, on the other hand, fare poorly when describing the observations, refuting previous claims that mass-dependent disruption of star clusters is observed in the LMC over the studied M–τ domain. Clusters in the SMC can be described by the same g(M, τ) distribution as for the LMC, but with smaller samples and hence larger uncertainties. The successful g(M, τ) model for clusters in the Magellanic Clouds is virtually the same as the one for clusters in the merging Antennae galaxies, but extends the domain of validity to lower masses and to older ages. This indicates that the dominant disruption processes are similar in these very different galaxies over at least τ ≲ 108 yr and possibly τ ≲ 109 yr. The mass functions for young clusters in the LMC are power laws, while that for ancient globular clusters is peaked. We show that the observed shapes of these mass functions are consistent with expectations from the simple evaporation model presented by McLaughlin & Fall.