Bootes矮球状星系动力学演化的模拟
Modelling the dynamical evolution of the Bootes dwarf spheroidal galaxy
摘要：
我们研究了最近发现的牧夫座矮球状星系（银河系卫星）的广泛可能的进化历史。通过N体模拟，我们遵循的演化可能的祖先星系的牧夫座星系的各种轨道在银河系的引力势。考虑的祖先涵盖了从无暗物质的星团到大质量暗物质主导的宇宙学模拟结果的范围。对于每一种类型的祖先和轨道，我们比较了10 Gyr后的残骸与今天观察到的Bootes的可观察特性。我们的研究表明，牧夫座的祖先一定是，现在仍然是，暗物质占主导地位。在一般情况下，我们的模型是无法重现所观察到的高速分散在牧夫座没有暗物质。我们的模型不支持随时间变化的潮汐效应作为一种机制，能够显着膨胀的内部速度分散。由于我们最初的球形模型都不能再现牧夫座的伸长，我们的研究结果表明，牧夫座的祖先可能有一些内在的扁平。虽然本文的重点是牧夫座矮球状体，这些模型可能是普遍相关的了解所有矮球状体星系的结构，稳定性和暗物质含量。
英文摘要：
We investigate a wide range of possible evolutionary histories for the recently discovered Bootes dwarf spheroidal galaxy, a Milky Way satellite. By means of N-body simulations we follow the evolution of possible progenitor galaxies of Bootes for a variety of orbits in the gravitational potential of the Milky Way. The progenitors considered cover the range from dark-matter-free star clusters to massive, dark-matter dominated outcomes of cosmological simulations. For each type of progenitor and orbit we compare the observable properties of the remnant after 10 Gyr with those of Bootes observed today. Our study suggests that the progenitor of Bootes must have been, and remains now, dark matter dominated. In general our models are unable to reproduce the observed high velocity dispersion in Bootes without dark matter. Our models do not support time-dependent tidal effects as a mechanism able to inflate significantly the internal velocity dispersion. As none of our initially spherical models is able to reproduce the elongation of Bootes, our results suggest that the progenitor of Bootes may have had some intrinsic flattening. Although the focus of the present paper is the Bootes dwarf spheroidal, these models may be of general relevance to understanding the structure, stability and dark matter content of all dwarf spheroidal galaxies.
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