Satellites of simulated galaxies: survival, merging and their relationto the dark and stellar haloes
Satellites of simulated galaxies: survival, merging and their relationto the dark and stellar haloes
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DOI：
10.1111/j.1365-2966.2007.12024.x
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发表时间：
2007-04
影响因子：
4.8
通讯作者：
L. Sales;J. Navarro;M. Abadi;M. Steinmetz
中科院分区：
文献类型：
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作者：
L. Sales;J. Navarro;M. Abadi;M. Steinmetz
我们研究了在一套N体/气体动力学模拟的星系形成在一个冷的暗物质宇宙中的卫星星系的人口。模拟解决了每个主机周围近10个最明亮的卫星，探测系统比主系统暗六到七个星等。我们发现暗物质和卫星群之间几乎没有空间或运动学上的偏差。包含一半卫星的半径与暗物质成分的半质量半径相当，卫星的速度色散是晕维里速度的良好指标; σ sat /V vir = 0.9 ± 0.2。应用于本星系群，这个结果表明银河系和M31的维里速度可能大大低于其盘组件的旋转速度;我们发现V MW vir = 109 ± 22 km s-1和V M31 vir = 138 ± 35 km s-1，而V MW rot = 220 km s-1和V M31 rot = 260 km s-1。虽然不确定性很大，但有趣的是，这两个估计值都明显低于一些半分析模型的预期，这些模型预测V vir和V rot之间的差异较小。模拟卫星和暗物质的详细运动学也很好的协议：两个组件显示出稳定下降的速度色散曲线和温和的径向各向异性的速度分布。相比之下，模拟星系的恒星晕，主要由恒星碎片从破坏的卫星，是运动学和空间不同的人口幸存的卫星。这是因为卫星作为一个自我约束实体的生存敏感地依赖于质量和吸积时间，幸存的卫星明显偏向于最近被星系吸积的低质量系统。我们的研究结果支持最近提出的银河系晕和银河系卫星中恒星之间系统差异的起源：银河系恒星晕的难以捉摸的“积木”平均更大，并且比自约束存活至今的矮星群更早地被吸积（和破坏）。
We study the population of satellite galaxies formed in a suite of N-body/gasdynamical simulations of galaxy formation in a A cold dark matter universe. The simulations resolve nearly 10 most luminous satellites around each host, and probe systems up to six or seven magnitudes fainter than the primary. We find little spatial or kinematic bias between the dark matter and the satellite population. The radius containing half of all satellites is comparable to the half-mass radius of the dark matter component, and the velocity dispersion of the satellites is a good indicator of the virial velocity of the halo; σ sat /V vir ∼0.9 ± 0.2. Applied to the Local Group, this result suggests that the virial velocity of the Milky Way and M31 might be substantially lower than the rotation speed of their disc components; we find V MW vir ∼109 ± 22 km s -1 and V M31 vir ∼ 138 ± 35 km s -1 , respectively, compared to V MW rot ∼220 km s -1 and V M31 rot ∼260 km s -1 . Although the uncertainties are large, it is intriguing that both estimates are significantly lower than expected from some semi-analytic models, which predict a smaller difference between V vir and V rot . The detailed kinematics of simulated satellites and dark matter are also in good agreement: both components show a steadily decreasing velocity dispersion profile and a mild radial anisotropy in their velocity distribution. By contrast, the stellar halo of the simulated galaxies, which consists predominantly of stellar debris from disrupted satellites, is kinematically and spatially distinct from the population of surviving satellites. This is because the survival of a satellite as a self-bound entity depends sensitively on mass and on time of accretion and surviving satellites are significantly biased toward low-mass systems that have been recently accreted by the galaxy. Our results support recent proposals for the origin of the systematic differences between stars in the Galactic halo and in Galactic satellites: the elusive 'building blocks' of the Milky Way stellar halo were on average more massive, and were accreted (and disrupted) earlier than the population of dwarfs that has survived self-bound until the present.