THE DUAL ORIGIN OF STELLAR HALOS
THE DUAL ORIGIN OF STELLAR HALOS
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DOI：
10.1088/0004-637x/702/2/1058
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发表时间：
2009-04
期刊：
影响因子：
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通讯作者：
A. Zolotov;B. Willman;A. Brooks;F. Governato;C. Brook;D. Hogg;T. Quinn;G. Stinson
中科院分区：
文献类型：
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作者：
A. Zolotov;B. Willman;A. Brooks;F. Governato;C. Brook;D. Hogg;T. Quinn;G. Stinson
我们用高分辨率的宇宙SPH+N体模拟研究了四个模拟盘状星系的恒星晕的形成。这些模拟包括对星系形成所涉及的所有主要物理过程的自洽处理。这里展示的每个模拟星系的总质量为∼1012M☉，但跨越了一系列合并历史。这些模拟使我们能够研究在Λcdm宇宙中原位恒星形成(在主星系中形成的恒星)和从次光晕中吸积恒星在建立恒星晕过程中的竞争重要性。所有四个模拟的星系都被一个恒星晕包围着，它的内部区域(r<；20kpc)既包含聚积的恒星，也包含原位的恒星群。星系晕的外部区域是通过纯粹的卫星吸积和分裂而聚集在一起的。大多数在高红移时形成的原位晕星是由星系势井内部1kpc的平稳吸积的冷气体形成的，可能是作为其原始圆盘的一部分。通过一系列的重大合并，这些恒星从它们的中心位置转移到了光晕中。我们发现，最近静止合并历史的两个星系的内晕中的原位恒星比例(∼20%-50%)高于最近合并的两个星系(∼5%-10%)。集中在银河系内晕中的恒星群的观测研究将最受具有晕运动学的原位恒星的存在的影响，因为我们发现它们存在于内几十KPC中是星系形成的一个普遍特征。
We investigate the formation of the stellar halos of four simulated disk galaxies using high-resolution, cosmological SPH + N-body simulations. These simulations include a self-consistent treatment of all the major physical processes involved in galaxy formation. The simulated galaxies presented here each have a total mass of ∼1012 M☉, but span a range of merger histories. These simulations allow us to study the competing importance of in situ star formation (stars formed in the primary galaxy) and accretion of stars from subhalos in the building of stellar halos in a ΛCDM universe. All four simulated galaxies are surrounded by a stellar halo, whose inner regions (r < 20 kpc) contain both accreted stars, and an in situ stellar population. The outer regions of the galaxies' halos were assembled through pure accretion and disruption of satellites. Most of the in situ halo stars formed at high redshift out of smoothly accreted cold gas in the inner 1 kpc of the galaxies' potential wells, possibly as part of their primordial disks. These stars were displaced from their central locations into the halos through a succession of major mergers. We find that the two galaxies with recently quiescent merger histories have a higher fraction of in situ stars (∼20%–50%) in their inner halos than the two galaxies with many recent mergers (∼5%–10% in situ fraction). Observational studies concentrating on stellar populations in the inner halo of the Milky Way will be the most affected by the presence of in situ stars with halo kinematics, as we find that their existence in the inner few tens of kpc is a generic feature of galaxy formation.