标题： 超大分子云形成超紧凑矮星系 显示英文标题

标题： Formation of ultra-compact dwarf galaxies from supergiant molecular clouds

摘要： 超紧凑矮星系（UCDs）的起源尚不清楚。 UCDs的一种可能形成路径是具有核心的椭圆矮星系（dE, N）的剥离，然而，这些大质量核心恒星系统的形成方式仍不清楚。 为了更好地建立UCDs的早期历史，我们利用流体动力学模拟研究从超巨大分子云（SGMCs）中形成UCD前体团块的形成过程。 在本研究中，我们关注质量为$10^{7} - 10^{8} \rm M_{\odot}$的SGMCs，这些SGMCs可以形成具有与UCDs相似物理特性的大质量恒星团块。 我们发现，这些团块具有两阶段的扩展恒星形成历史，产生多个不同的恒星种群，并且恒星形成率依赖于超新星和AGB恒星的反馈效应。 这些团块中后期形成的恒星更加致密，导致明显嵌套的结构，并且这些恒星将比第一代恒星更富He，从而导致轻微的颜色梯度。 模拟的团块展示了$R_{\rm eff}$与$M$以及$\sigma_{v}$与$M$之间的尺度关系，这些关系与观测到的UCDs一致，并且与原始SGMC的关系高度一致。 我们讨论这类SGMC是否可以通过高红移星系中自引力分子云的合并形成。 显示英文摘要

摘要： The origin of ultra-compact dwarf galaxies (UCDs) is not yet clear. One possible formation path of UCDs is the threshing of a nucleated elliptical dwarf galaxy (dE, N), however, it remains unclear how such massive nuclear stellar systems were formed in dwarf galaxies. To better establish the early history of UCDs, we investigate the formation of UCD progenitor clusters from super giant molecular clouds (SGMCs), using hydrodynamical simulations. In this study we focus on SGMCs with masses $10^{7} - 10^{8} \rm M_{\odot}$ that can form massive star clusters that display physical properties similar to UCDs. We find that the clusters have extended star formation histories with two phases, producing multiple distinct stellar populations, and that the star formation rate is dependent on the feedback effects of SNe and AGB stars. The later generations of stars formed in these clusters are more compact, leading to a clearly nested structure, and these stars will be more He-rich than those of the first generation, leading to a slight colour gradient. The simulated clusters demonstrate scaling relations between $R_{\rm eff}$ and $M$ and $\sigma_{v}$ and $M$ consistent with those observed in UCDs and strongly consistent with those of the original SGMC. We discuss whether SGMCs such as these can be formed through merging of self-gravitating molecular clouds in galaxies at high-z.