Evidence for halo kinematics among cool carbon-rich dwarfs
Evidence for halo kinematics among cool carbon-rich dwarfs
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DOI：
10.1093/mnras/sty890
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发表时间：
2018-04
影响因子：
4.8
通讯作者：
J. Farihi;A. R. Arendt;H. S. Machado;L. J. Whitehouse
中科院分区：
文献类型：
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作者：
J. Farihi;A. R. Arendt;H. S. Machado;L. J. Whitehouse
这篇论文报告了初步的，但令人信服的，对N > 600富含碳的矮星的运动学推断，表明大约30- 60%是银河晕的成员。该研究使用了SDSS中光谱和非运动学选择的恒星样本，并将这些数据与基于Gaia DR1天体测量的三个固有运动目录交叉关联，以产生它们的三维空间速度估计。根据有限数量的视差测量，具有晕状运动的恒星的比例大约是30%，其余的由厚盘主导，但接近60%的样本位于一个古老的，金属贫乏的盘等时线以下，以减少的适当运动。一个古老的种群与冷矮星中C/O bbb10的外在起源是一致的，在冷矮星中，固定质量的碳污染更容易超越较低的氧丰度，并且缺乏来自年轻白矮星同伴的可探测的紫外光蓝通量。由于初始恒星质量函数倾向于像银河盘那样的低质量恒星，dC恒星很可能是银河系中碳增强、金属缺乏恒星的主要来源。
This paper reports preliminary, yet compelling, kinematical inferences for N ≳ 600 carbonrich dwarf stars that demonstrate around 30-60 per cent are members of the Galactic halo. The study uses a spectroscopically and non-kinematically selected sample of stars from the SDSS, and cross-correlates these data with three proper motion catalogues based on Gaia DR1 astrometry to generate estimates of their 3D space velocities. The fraction of stars with halo-like kinematics is roughly 30 per cent for distances based on a limited number of parallax measurements, with the remainder dominated by the thick disc, but close to 60 per cent of the sample lies below an old, metal-poor disc isochrone in reduced proper motion. An ancient population is consistent with an extrinsic origin for C/O > 1 in cool dwarfs, where a fixed mass of carbon pollution more readily surmounts lower oxygen abundance and with a lack of detectable ultraviolet-blue flux from younger white dwarf companions. For an initial stellar mass function that favours low-mass stars as in the Galactic disc, the dC stars are likely to be the dominant source of carbon-enhanced, metal-poor stars in the Galaxy.