On the formation of dwarf galaxies and stellar haloes
On the formation of dwarf galaxies and stellar haloes
复制标题
关于矮星系和恒星晕的形成
DOI：
10.1111/j.1365-2966.2006.10720.x
复制
发表时间：
2006
影响因子：
4.8
通讯作者：
M. Viel
中科院分区：
文献类型：
--
作者：
Justin I. Read;A. Pontzen;M. Viel;M. Viel
使用分析论证和一套非常高分辨率（∼10 3 M/粒子）宇宙流体动力学模拟，我们认为高红移，z∼10，M∼10 8 Mhaloes，形成了星系形成的最小“重子构建块”（BBB）。这些晕的质量足以通过原子线冷却有效地形成恒星，并在超新星（SN）风和再电离存在的情况下保留其气体。这些综合效应，特别是 SN 反馈的效应，产生了急剧的转变：在 3-10 × 10 7 M� 的质量范围内，BBB 的恒星质量下降了两个数量级。低于 ∼2 × 10 7 M� ，星系将是黑暗的，几乎没有恒星，也没有气体。在此尺度之上是星系形成的最小单位：BBB。我们表明 BBB 具有球状、低旋转速度、古老且金属贫乏的恒星分布：它们类似于本星系群 (LG) 的矮球状星系 (dSphs)。然而，与 LG dSph 不同的是，它们含有大量气体成分。我们使用线性理论将这些高红移 BBB 与 z = 0 处观测到的最小矮星系联系起来。这些处于高红移的富含气体的 BBB 的一小部分（~100）落入银河系 (MW) 大小的星系中。我们建议其中 10% 幸存下来，成为目前观测到的 LG 矮星系。这与最近的数值估计是一致的。那些在良性轨道上坠落的光环使它们远离中波星系或仙女座星系，它们设法保留它们的气体并慢慢形成恒星——它们成为最小的矮不规则星系；那些在更严重轨道上的气体失去气体的速度比它们形成恒星并成为矮球体的速度快。其余 90% 的 BBB 将被累积。我们证明这给出了与 MW 旧恒星晕一致的金属丰度和总恒星质量。
Using analytic arguments and a suite of very high resolution (∼10 3 Mper particle) cosmo- logical hydrodynamical simulations, we argue that high-redshift, z ∼ 10, M ∼ 10 8 Mhaloes, form the smallest 'baryonic building block' (BBB) for galaxy formation. These haloes are just massive enough to efficiently form stars through atomic line cooling and to hold on to their gas in the presence of supernova (SN) winds and reionization. These combined effects, in par- ticular that of the SN feedback, create a sharp transition: over the mass range 3-10 × 10 7 M� , the BBBs drop two orders of magnitude in stellar mass. Below ∼2 × 10 7 M� , galaxies will be dark with almost no stars and no gas. Above this scale is the smallest unit of galaxy formation: the BBB. We show that the BBBs have stellar distributions which are spheroidal, of low rotational velocity, old and metal poor: they resemble the dwarf spheroidal galaxies (dSphs) of the Local Group (LG). Unlike the LG dSphs, however, they contain significant gas fractions. We connect these high-redshift BBBs to the smallest dwarf galaxies observed at z = 0 using linear theory. A small fraction (∼100) of these gas-rich BBBs at high redshift fall in to a galaxy the size of the Milky Way (MW). We suggest that 10 per cent of these survive to become the observed LG dwarf galaxies at the present epoch. This is consistent with recent numerical estimates. Those infalling haloes on benign orbits which keep them far away from the MW or Andromeda manage to retain their gas and slowly form stars - these become the smallest dwarf irregular galaxies; those on more severe orbits lose their gas faster than they can form stars and become the dwarf spheroidals. The remaining 90 per cent of the BBBs will be accreted. We show that this gives a metallicity and total stellar mass consistent with the MW old stellar halo.