论文标题
开放恒星簇的潮汐尾巴作为早期气体驱动I的探针I：半分析模型
Tidal tails of open star clusters as probes to early gas expulsion I: A semi-analytic model
论文作者
论文摘要
恒星簇从红色乌云的最密集的部分形成。巨大恒星的出现驱逐了尚未形成恒星的残留气体。燃气驱动会降低嵌入式簇的重力潜力，从而解开许多簇星。然后，这些恒星在星系的外部重力场中移动自己的轨迹，形成潮汐尾巴。我们研究了由于在气体驱动的各种情况下驱逐原始气体而导致的潮汐尾巴形成的形成和演变，以提供对动态进化（> 100> 100 MYR）银河系簇周围的潮汐尾巴的预测，这可能由Gaia Mission检测到。我们为尾部演化提供了半分析模型。我们发现，在燃气驱动过程中释放的潮汐尾巴具有不同的运动学特性，与由于蒸发而逐渐形成的尾巴。燃气驱动潮汐尾巴随时间表现出非单调的膨胀，其中较长的膨胀时期散布在较短的收缩时期。尾部厚度和速度分散量很大，但不完全定期，随时间而变化。尾部厚度和速度分散体的最小值仅由银河电位的性质而不是由簇的性质给出。 （半）分析模型对尾巴的范围，尾部厚度和速度分散体提供的估计值与Nbody6模拟非常吻合。这意味着半分析模型可用于估算给定年龄和轨道参数群的气体驱动潮汐尾部的性质，而无需进行数值模拟。在后续纸上进行了初始条件的参数空间更扩展的研究。
Star clusters form out of the densest parts of infrared dark clouds. The emergence of massive stars expels the residual gas, which has not formed stars yet. Gas expulsion lowers the gravitational potential of the embedded cluster, unbinding many of the cluster stars. These stars then move on their own trajectories in the external gravitational field of the Galaxy, forming a tidal tail. We investigate the formation and evolution of the tidal tail forming due to expulsion of primordial gas under various scenarios of gas expulsion to provide predictions for tidal tails around dynamically evolved (age > 100 Myr) galactic star clusters, which can be possibly detected by the Gaia mission. We provide a semi-analytical model for the tail evolution. We find that tidal tails released during gas expulsion have different kinematic properties than the tails gradually forming due to evaporation. The gas expulsion tidal tail shows non-monotonic expansion with time, where longer epochs of expansion are interspersed with shorter epochs of contraction. The tail thickness and velocity dispersions strongly, but not exactly periodically, vary with time. The times of minima of tail thickness and velocity dispersions are given only by the properties of the galactic potential, and not by the properties of the cluster. The estimates provided by the (semi-)analytical model for the extent of the tail, the minima of tail thickness, and velocity dispersions are in a very good agreement with the nbody6 simulations. This implies that the semi-analytic model can be used for estimating the properties of the gas expulsion tidal tail for a cluster of a given age and orbital parameters without the necessity of performing numerical simulations. A study with a more extended parameter space of the initial conditions is performed in the follow up paper.
