论文标题
M54的暗物质光环
The Dark Matter Halo of M54
论文作者
论文摘要
M54是嵌入暗物质光环中的球状簇的原型。 Gaia EDR3光度法和正确的运动将旧的，贫困的星星与更丰富和年轻的矮人星系星分开。金属贫穷的星星主导着内部的50 pc，其速度分散曲线最低降至30 pc，然后恢复到几乎中央速度分散体，正如在暗物质光环的中心的球状簇所期望的那样。对这三个独立恒星种群的牛仔裤分析给出了一致的质量，这些质量大致在半径上呈线性上升至1 kpc，这意味着一个小的核心或cuspy光环。这些数据与在50 kpc papocenter 2.3 Gyr的50 kpc Apocenter下降低至3x10^8 m_sun的插入CDM暗物质光环兼容。潮汐逐渐清除了1 kpc以上的材料，但对恒星和中心300 pc内的暗物质几乎没有影响。 M54似乎是带有和没有局部暗光晕的球状簇之间的过渡系统，其在银河系内的演变敏感地取决于积聚和轨道周围的时间。
M54 is a prototype of a globular cluster embedded in a dark matter halo. Gaia EDR3 photometry and proper motions separate the old, metal-poor stars from the more metal rich and younger dwarf galaxy stars. The metal poor stars dominate the inner 50 pc, with a velocity dispersion profile that declines to a minimum around 30 pc then rises back to nearly the central velocity dispersion, as expected for a globular cluster at the center of a dark matter halo. The Jeans analysis of the three separate stellar populations give consistent masses that rise approximately linearly with radius to 1 kpc, implying a small core or cuspy halo. These data are compatible with an infalling CDM dark matter halo reduced to 3x10^8 M_sun at the 50 kpc apocenter 2.3 Gyr ago, with a central globular cluster surrounded by the remnant of a dwarf galaxy. Tides gradually remove material beyond 1 kpc but have little effect on the stars and dark matter within 300 pc of the center. M54 appears to be a transitional system between globular clusters with and without local dark halos, whose evolution within the galaxy depends sensitively on the time of accretion and orbital pericenter.
