The formation and hierarchical assembly of globular cluster populations
The formation and hierarchical assembly of globular cluster populations
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DOI：
10.1093/mnras/sty3007
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发表时间：
2018-05
影响因子：
4.8
通讯作者：
K. El-Badry;E. Quataert;D. Weisz;Nick Choksi;M. Boylan-Kolchin
中科院分区：
文献类型：
--
作者：
K. El-Badry;E. Quataert;D. Weisz;Nick Choksi;M. Boylan-Kolchin
我们使用建立在暗物质合并树上的球状星团(GC)形成的半解析模型来探索形成物理和等级组装在决定GC群体性质方面的相对作用。许多以前的工作认为，观测到的GC总质量和晕质量之间的线性关系指向了GC-暗物质之间的基本联系，或者表明GC在反馈过程引入重子到暗物质质量关系中的非线性之前，在很高的红移处形成了GC。我们证明了在M_rm vir}(z=0)\gtrsim 10^{11.5}M_(11.5)M_(Odot)}时，晕质量与GC总质量之比的恒定实际上是层级组装的必然结果：根据中心极限定理，它与GC形成时的GC-晕质量关系无关。在$M{rm vir}(z=0)<；10^{11.5}M{\odot}$处的GC-晕质量关系对GC形成过程的细节更为敏感。在我们的基准模型中，当气体面密度超过临界值时，星系中就会形成GC。这个模型自然地预测了与在附近星系中观察到的类似的双峰GC颜色分布，并重现了观察到的GC系统金属丰度与晕质量之间的关系。它预测宇宙GC的形成速率在$z$$\sim$4达到峰值，太晚了，以至于GC在再电离过程中无法对UV光度密度做出显著贡献。
We use a semi-analytic model for globular cluster (GC) formation built on dark matter merger trees to explore the relative role of formation physics and hierarchical assembly in determining the properties of GC populations. Many previous works have argued that the observed linear relation between total GC mass and halo mass points to a fundamental GC -- dark matter connection or indicates that GCs formed at very high redshift before feedback processes introduced nonlinearity in the baryon-to-dark matter mass relation. We demonstrate that at $M_{\rm vir}(z=0) \gtrsim 10^{11.5} M_{\odot}$, a constant ratio between halo mass and total GC mass is in fact an almost inevitable consequence of hierarchical assembly: by the central limit theorem, it is expected at $z=0$ independent of the GC-to-halo mass relation at the time of GC formation. The GC-to-halo mass relation at $M_{\rm vir}(z=0) < 10^{11.5} M_{\odot}$ is more sensitive to the details of the GC formation process. In our fiducial model, GC formation occurs in galaxies when the gas surface density exceeds a critical value. This model naturally predicts bimodal GC color distributions similar to those observed in nearby galaxies and reproduces the observed relation between GC system metallicity and halo mass. It predicts that the cosmic GC formation rate peaked at $z$ $\sim$ 4, too late for GCs to contribute significantly to the UV luminosity density during reionization.