The Accretion Origin of the Milky Way’s Stellar Halo
The Accretion Origin of the Milky Way’s Stellar Halo
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DOI：
10.1086/588032
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发表时间：
2007-05
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影响因子：
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通讯作者：
E. Bell;D. Zucker;V. Belokurov;Sanjib Sharma;K. Johnston;J. Bullock;D. Hogg;K. Jahnke;J. D.
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文献类型：
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作者：
E. Bell;D. Zucker;V. Belokurov;Sanjib Sharma;K. Johnston;J. Bullock;D. Hogg;K. Jahnke;J. D.
我们使用斯隆数字巡天（SDSS）数据发布5的数据，使用约400万颗0.2 α > − 4的色选主序星来探索银河系恒星晕的整体结构和子结构。然而，我们发现，所有光滑和对称的模型是非常差的适合恒星晕星的分布，因为数据表现出大量的空间子结构。在考虑了泊松不确定性的（已知）贡献后，我们使用模型轮廓周围尺度为100 pc的数据均方根量化了与光滑扁圆/三轴模型的偏差。在SDSS的DR 5区域内，实际恒星分布与任何平滑的参数化晕模型的均方根偏差σ/total为1.40%：因此，恒星晕是高度结构化的。我们比较了观测与模拟的银河系恒星晕形成完全从吸积的卫星在宇宙学的背景下，通过分析模拟以同样的方式作为SDSS数据。虽然模拟的恒星晕的质量、整体轮廓和亚结构程度显示出相当大的分散性，但银河系晕的亚结构性质和程度与完全由破裂的卫星星系碎片建造的“典型”恒星晕的性质相匹配。因此，我们的研究结果指向这样一幅图景，即银河系的恒星晕中有很大一部分是由卫星星系吸积而来的。
We have used data from the Sloan Digital Sky Survey (SDSS) Data Release 5 to explore the overall structure and substructure of the stellar halo of the Milky Way using ~4 million color-selected main-sequence turnoff stars with 0.2 α > − 4. Yet, we found that all smooth and symmetric models were very poor fits to the distribution of stellar halo stars because the data exhibit a great deal of spatial substructure. We quantified deviations from a smooth oblate/triaxial model using the rms of the data around the model profile on scales ≳100 pc, after accounting for the (known) contribution of Poisson uncertainties. Within the DR5 area of the SDSS, the fractional rms deviation σ/total of the actual stellar distribution from any smooth, parameterized halo model is ≳40%: hence, the stellar halo is highly structured. We compared the observations with simulations of galactic stellar halos formed entirely from the accretion of satellites in a cosmological context by analyzing the simulations in the same way as the SDSS data. While the masses, overall profiles, and degree of substructure in the simulated stellar halos show considerable scatter, the properties and degree of substructure in the Milky Way’s halo match well the properties of a “typical” stellar halo built exclusively out of the debris from disrupted satellite galaxies. Our results therefore point toward a picture in which an important fraction of the stellar halo of the Milky Way has been accreted from satellite galaxies.