Unmixing the Galactic halo with RR Lyrae tagging
Unmixing the Galactic halo with RR Lyrae tagging
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DOI：
10.1093/mnras/sty615
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发表时间：
2017-11
影响因子：
4.8
通讯作者：
V. Belokurov;A. Deason;Sergey E. Koposov;M. Catelán;D. Erkal;A. Drake;N. Evans
中科院分区：
文献类型：
--
作者：
V. Belokurov;A. Deason;Sergey E. Koposov;M. Catelán;D. Erkal;A. Drake;N. Evans
我们表明，标记RR天琴座恒星根据其位置的周期振幅图可以用来阐明银河系恒星晕的成因。AB型RR天琴座的混合物，沿着奥斯特霍夫提出的线沿着分成几类，显示出与银心半径的强烈和连贯的演化。RR天琴座组成的变化似乎与晕的径向密度分布在1.25 kpc处的断裂相吻合。使用简单的恒星晕模型，我们建立了至少三种不同类型的吸积事件是必要的，以解释所观察到的RRab行为。鉴于存在的RRab类分数和总恒星含量的矮卫星之间的相关性，我们假设，场晕RRab组成控制的质量的祖贡献的大部分的恒星碎片在给定的半径。这个想法是测试对一套宇宙学放大模拟银河系般的恒星晕形成。最后，我们研究了银河系晕中一些最突出的恒星流，并证明了它们的RRab类分数遵循先前建立的趋势。
We show that tagging RR Lyrae stars according to their location in the period-amplitude diagram can be used to shed light on the genesis of the Galactic stellar halo. The mixture of RR Lyrae of ab type, separated into classes along the lines suggested by Oosterhoff, displays a strong and coherent evolution with Galactocentric radius. The change in the RR Lyrae composition appears to coincide with the break in the halo’s radial density profile at ∼25 kpc. Using simple models of the stellar halo, we establish that at least three different types of accretion events are necessary to explain the observed RRab behavior. Given that there exists a correlation between the RRab class fraction and the total stellar content of a dwarf satellite, we hypothesize that the field halo RRab composition is controlled by the mass of the progenitor contributing the bulk of the stellar debris at the given radius. This idea is tested against a suite of cosmological zoom-in simulations of Milky Way-like stellar halo formation. Finally, we study some of the most prominent stellar streams in the Milky Way halo and demonstrate that their RRab class fractions follow the trends established previously.