arXiv 1607.035772016-07-13astro-ph.GA

合并星系NGC 3256中团簇形成和毁灭

Star Cluster Formation and Destruction in the Merging Galaxy NGC 3256

Alexander J. Mulia, Rupali Chandar, Bradley C. Whitmore

备注：: 18 pages, 15 figures, accepted for publication in ApJ. Image quality on some figures has been degraded to comply with arxiv file limitations
DOI：: 10.3847/0004-637X/826/1/32

摘要：

我们使用哈勃太空望远镜上的高级巡天相机来研究NGC 3256主体中年轻大质量星团的丰富人口，NGC 3256是一对合并的星系，具有高恒星形成率（SFR）和单位面积SFR（$Σ_{\rm{SFR}}$）。这些星系团的光度和质量函数遵循幂律，对于$τ< 10$ Myr星系团，$dN/dL \propto L^α$与$α= -2.23 \pm 0.07$，$dN/dM \propto M^β$与$β= -1.86 \pm 0.34$，类似于在更静止的星系中发现的。年龄分布可以用$dN/dτ\propto τ^ γ$来描述，$γ\approx -0.67 \pm 0.08$代表年龄小于几亿年的星系团，与星系团的质量没有明显的关系。这与星团中的$\sim 80 \%$每十年被破坏一次的情况是一致的。通过测定NGC 3256的束缚星系团中恒星的比例（$Γ$）和CMF/SFR统计量（CMF是星系团的质量函数），并与其他星系的结果进行比较，我们研究了具有高$Σ_{\rm{SFR}}$的星系比静止星系更有效地形成星系团的说法。我们发现，NGC 3256的CMF/SFR统计数据与具有$Σ_{\rm{SFR}}$和SFR的星系的统计数据一致，这些星系的统计数据低于$1-3$的数量级，但只有当应用相同的假设时，对$Γ$的估计才是稳健的。目前，文献中可用的$Γ$值使用了不同的假设，这使得比较星系之间的结果更加困难。

英文摘要：

We use the Advanced Camera for Surveys on the Hubble Space Telescope to study the rich population of young massive star clusters in the main body of NGC 3256, a merging pair of galaxies with a high star formation rate (SFR) and SFR per unit area ($Σ_{\rm{SFR}}$). These clusters have luminosity and mass functions that follow power laws, $dN/dL \propto L^α$ with $α= -2.23 \pm 0.07$, and $dN/dM \propto M^β$ with $β= -1.86 \pm 0.34$ for $τ< 10$ Myr clusters, similar to those found in more quiescent galaxies. The age distribution can be described by $dN/dτ\propto τ^ γ$, with $γ\approx -0.67 \pm 0.08$ for clusters younger than about a few hundred million years, with no obvious dependence on cluster mass. This is consistent with a picture where $\sim 80 \%$ of the clusters are disrupted each decade in time. We investigate the claim that galaxies with high $Σ_{\rm{SFR}}$ form clusters more efficiently than quiescent systems by determining the fraction of stars in bound clusters ($Γ$) and the CMF/SFR statistic (CMF is the cluster mass function) for NGC 3256 and comparing the results with those for other galaxies. We find that the CMF/SFR statistic for NGC 3256 agrees well with that found for galaxies with $Σ_{\rm{SFR}}$ and SFRs that are lower by $1-3$ orders of magnitude, but that estimates for $Γ$ are only robust when the same sets of assumptions are applied. Currently, $Γ$ values available in the literature have used different sets of assumptions, making it more difficult to compare the results between galaxies.

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英文摘要：

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