arXiv 0804.19192008-04-11astro-ph

什么是星系？冷暗物质有多冷？近场宇宙学的新进展

What is a galaxy? How Cold is Cold Dark Matter? Recent progress in Near Field Cosmology

Gerard Gilmore, Dan Zucker, Mark Wilkinson, Rosemary F. G. Wyse, Vasily Belokurov, Jan Kleyna, Andreas Koch, N. Wyn Evans, Eva K. Grebel

备注：: proceedings of The 1st Subaru International Conference, "Panoramic Views of Galaxy Formation and Evolution" (Hayama, Japan, 11-16 Dec 2007) ASP Conf ser

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摘要：

最近，星团、超致密矮星、星系核和局部dSph星系的光度和运动学数据有了很大的改进，斯巴鲁特别对光度研究做出了重大贡献。这些数据显示，在半光半径上有一个双峰分布，稳定的星团总是小于35 pc，而稳定的星系总是大于120 pc。我们扩展了以前已知的观测关系，并解释他们在一个更基本的一对内在属性的暗物质本身：暗物质形成核心质量分布，与核心尺度长度大于约100 pc，总是有一个最大的中心质量密度与一个狭窄的范围。dSph星系中的暗物质似乎是聚集在一起的，因此在恒星分布中有一个平均体积质量密度，其值非常低，约为0.1 $M_{\odot}$ pc $^{-3}$。没有一个dSphs显示需要存在内部尖点的运动学，而在两个dSphs中，有证据表明内部区域的密度分布较浅（核心）。最大的中心暗物质密度取决于模型，但可能有一个平均值（在半径为10 pc的体积上平均）约为0.1 $M_{\odot}$ pc $^{-3}$，即5 GeV/c $^2$ cm $^{-3}$）。银河系嵌入在具有这些性质的暗物质晕中;没有观察到包含暗物质的较小系统。

英文摘要：

There has been a vast recent improvement in photometric and kinematic data for star clusters, Ultra Compact dwarfs, galactic nuclei, and local dSph galaxies, with Subaru contributing substantially to the photometric studies in particular. These data show that there is a bimodal distribution in half-light radii, with stable star clusters always being smaller than 35pc, while stable galaxies are always larger than 120pc. We extend the previously known observational relationships and interpret them in terms of a more fundamental pair of intrinsic properties of dark matter itself: dark matter forms cored mass distributions, with a core scale length of greater than about 100pc, and always has a maximum central mass density with a narrow range. The dark matter in dSph galaxies appears to be clustered such that there is a mean volume mass density within the stellar distribution which has the very low value of about 0.1$M_{\odot}$ pc$^{-3}$. None of the dSphs displays kinematics which require the presence of an inner cusp, while in two dSphs there is evidence that the density profile is shallow (cored) in the inner regions. The maximum central dark matter density derived is model dependent, but is likely to have a mean value (averaged over a volume of radius 10pc) of about 0.1$M_{\odot}$ pc$^{-3}$, which is 5GeV/c$^2$cm$^{-3}$). Galaxies are embedded in dark matter halos with these properties; smaller systems containing dark matter are not observed.

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