原始调查XVIII：C-19：暗物质主导的球状星团的潮汐碎片？
The Pristine survey XVIII: C-19: Tidal debris of a dark matter-dominated globular cluster?
摘要：
最近发现的C-19恒星流是银河系晕中运动学相关的贫金属恒星的集合，缺乏明显的祖先。该流在天空中跨越约15度的弧，轨道拟合表明其离心距离约为20 kpc，近心点约为10 kpc。可用光谱的恒星的金属丰度分布窄，加上轻元素丰度的变化，表明球状星团（GC）的起源。然而，所观察到的金属丰度（[Fe/H] ~ -3.4）远低于任何已知的GC。此外，该流的宽度和速度分散度与预期的破坏矮星系的情况相似，并且远远大于能够破坏C-19轨道的GC潮汐碎片。我们在这里提出了一个非传统的模型，其中的C-19祖是一个暗物质为主的恒星系统与GC样丰度模式。我们使用N体模拟表明，潮汐破坏的~100 pc国王模型恒星组件嵌入在一个~20公里/秒的尖状冷暗物质晕产生的碎片与C-19的观察到的宽度和速度色散。这颗母星的恒星成分被完全破坏，分散在两个不同的星系流中;一个对应于C-19，另一个可能隐藏在银河系平面后面。如果这样的伴流被发现，这将表明暗物质主导的矮星也可能发展出类似GC的富集模式，这一发现将为我们理论上理解GC和矮星系中多个种群的形成提供信息。
英文摘要：
The recently discovered C-19 stellar stream is a collection of kinematically associated metal-poor stars in the halo of the Milky Way lacking an obvious progenitor. The stream spans an arc of ~15 degrees in the sky, and orbit-fitting suggests an apocentric distance of ~20 kpc and a pericentre of ~10 kpc. The narrow metallicity dispersion of stars with available spectra, together with light element abundance variations, suggests a globular cluster (GC) origin. The observed metallicity ([Fe/H] ~ -3.4), however, is much lower than that of any known GC. In addition, the width and velocity dispersion of the stream are similar to those expected from disrupting dwarf galaxies, and substantially larger than the tidal debris of GCs able to disrupt on C-19's orbit. We propose here an unconventional model where the C-19 progenitor is a dark matter-dominated stellar system with GC-like abundance patterns. We use N-body simulations to show that the tidal disruption of a ~100 pc King-model stellar component embedded in a ~20 km/s cuspy cold dark matter halo yields debris consistent with C-19's observed width and velocity dispersion. The stellar component of the progenitor is fully disrupted, and is spread over two distinct streams; one corresponding to C-19 and another possibly hiding behind the Galactic plane. If such companion stream were found, it would suggest that dark matter-dominated dwarfs may also develop GC-like enrichment patterns, a finding that would inform our theoretical understanding of the formation of multiple populations in GCs and dwarf galaxies alike.
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