The origin of failed subhaloes and the common mass scale of the Milky Way satellite galaxies
The origin of failed subhaloes and the common mass scale of the Milky Way satellite galaxies
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DOI：
10.1111/j.1745-3933.2009.00748.x
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发表时间：
2009-09
影响因子：
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通讯作者：
T. Okamoto;Carlos S. Frenk Tsukuba;Durham
中科院分区：
文献类型：
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作者：
T. Okamoto;Carlos S. Frenk Tsukuba;Durham
我们研究卫星星系的形成历史和今天的结构，形成在一个高分辨率的流体动力学模拟银河系。模拟卫星的亮度跨度接近4个数量级，但它们内部的质量非常相似，约3 × 107 M⊙，散射很小。这一结果与Strigari等人最近对银河系中矮球状星系（dSphs）的测量结果一致。在我们的模拟中，理想的质量尺度自然产生于气体早期再电离的影响。这些对光环的圆速度施加了~ 12 km s−1的急剧阈值，晕可以冷却气体并形成恒星。目前，拥有与经典银河系矮星（LV≥2.6 × 105 L⊙）一样明亮的卫星的亚晕通常已经成长为圆周速度≥20 km s−1。然而，今天也有具有类似圆周速度的亚晕，然而，低于再电离的阈值，因此仍然是黑暗的。当晕被吸积到主星系祖先中时，阈值以上的晕的恒星形成被截断。因此，今天矮卫星的许多特性，如亮度和恒星形成速率，都是由它们的吸积时间决定的。
We study the formation histories and present-day structure of satellite galaxies formed in a high-resolution hydrodynamic simulation of a Milky Way like galaxy. The simulated satellites span nearly four orders of magnitude in luminosity but have a very similar mass within their inner 600 pc, ∼3 × 107 M⊙, with very little scatter. This result is in agreement with the recent measurements for dwarf spheroidal galaxies (dSphs) in the Milky Way by Strigari et al. In our simulations, a preferred mass scale arises naturally from the effects of the early re-ionization of gas. These impose a sharp threshold of ∼12 km s−1 on the circular velocity of haloes which can cool gas and make stars. At the present day, subhaloes that host satellites as luminous as the classical Milky Way dwarfs (LV≥ 2.6 × 105 L⊙) have typically grown to have circular velocities of ≳20 km s−1. There are, however, subhaloes with similar circular velocities today which were, nevertheless, below threshold at re-ionization and thus remain dark. Star formation in above-threshold haloes is truncated when the halo is accreted into the main galaxy progenitor. Thus, many properties of today's dwarf satellites such as their luminosity and star formation rate are set by their accretion time.