太小而不能成功：在低质量晕中维持恒星形成的困难
Too small to succeed: the difficulty of sustaining star formation in low-mass haloes
摘要：
我们提出了高分辨率的模拟一个孤立的矮球状（dSph）星系之间的红移$z\sim10$和$z\sim 4$，时代时，几个银河系dSph卫星经历了扩展的恒星形成，为了详细了解的物理过程，影响低质量的晕的能力，保留气体。众所周知，超新星反馈对于从$3\times 10^7$ M $_\odot$晕中排出气体是非常有效的，$_\odot$晕是质量为$\sim10^9$ M $_\odot$的红移0晕的典型红移10祖先的质量。我们调查的条件下，这样的晕是能够保留足够的高密度气体，以支持扩展的恒星形成。特别是，我们探讨的影响：增加相对浓度的气体相比，暗物质;更高浓度的暗物质晕;显着降低超新星速率;增强金属冷却由于从早期超新星富集。我们发现，盘状气体分布保留更多的气体比球形的，主要是由于较短的气体冷却时间在磁盘。然而，与标准初始质量函数相比，超新星的数量仍然需要显着减少，以允许保留高密度气体。我们的结论是，所观察到的dSphs的祖先只会保留维持恒星形成所需的气体，如果他们的质量，浓度和气体形态已经不寻常的dSphs质量晕祖细胞的红移为10。
英文摘要：
We present high resolution simulations of an isolated dwarf spheroidal (dSph) galaxy between redshifts $z\sim10$ and $z\sim 4$, the epoch when several Milky Way dSph satellites experienced extended star formation, in order to understand in detail the physical processes which affect a low-mass halo's ability to retain gas. It is well-established that supernova feedback is very effective at expelling gas from a $3\times 10^7$M$_\odot$ halo, the mass of a typical redshift 10 progenitor of a redshift 0 halo with mass $\sim10^9$M$_\odot$. We investigate the conditions under which such a halo is able to retain sufficient high-density gas to support extended star formation. In particular, we explore the effects of: an increased relative concentration of the gas compared to the dark matter; a higher concentration dark matter halo; significantly lower supernova rates; enhanced metal cooling due to enrichment from earlier supernovae. We show that disk-like gas distributions retain more gas than spherical ones, primarily due to the shorter gas cooling times in the disk. However, a significant reduction in the number of supernovae compared to that expected for a standard initial mass function is still needed to allow the retention of high density gas. We conclude that the progenitors of the observed dSphs would only have retained the gas required to sustain star formation if their mass, concentration and gas morphology were already unusual for those of a dSph-mass halo progenitor by a redshift of 10.
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