Stellar kinematics and interstellar turbulence
Stellar kinematics and interstellar turbulence
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恒星运动学和星际湍流
DOI：
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发表时间：
1979
期刊：
影响因子：
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通讯作者：
R. Larson
中科院分区：
文献类型：
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作者：
R. Larson
众所周知，邻近恒星的速度色散随着年龄的增长而系统地增加，这一事实通常通过假设恒星与大质量气体云相遇而随机加速来解释（Spitzer & Schwarzschild 1951，1953;维伦1977）。然而，相当古老的运动恒星群的明显存在，对随机加速度可能的作用提供了强有力的限制（埃根，1969;波义耳和麦克卢尔，1975）。另一种解释（Tinsley & Larson 1978）是年龄依赖性的速度色散的恒星年龄超过10岁1 S产生的星际湍流运动的时间逐渐衰减，如可信的崩溃模型预测。这种效应不能直接解释观测到的年龄小于10年的恒星的速度色散随年龄的变化，但Tinsley和Larson认为，如果最年轻恒星的速度色散只反映了气体的局部湍流运动，而较老恒星的速度色散则反映了银河系气体层中更大尺度的非圆形运动，那么这可以解释。如果星际介质具有一个运动的层次，其速度色散随所考虑的区域的大小而增加，那么自形成以来旅行得更远的老恒星将在更大体积的空间中采样气体运动，因此将比年轻恒星具有更大的速度色散。
It is well known that the velocity dispersion of nearby stars increases systematically with age, and this fact is conventionally explained by postulating that stars are randomly accelerated by encounters with massive gas clouds (Spitzer & Schwarzschild 1951, 1953; Wielen 1977). However, a strong constraint on the possible role of random accelerations is provided by the apparent existence of fairly old moving groups of stars (Eggen 1969, Boyle & McClure 1975). An alternative explanation (Tinsley & Larson 1978) is that the age dependence of the velocity dispersion of stars older than 10 yr 1 S produced by a gradual decay with time of interstellar turbulent motions, as predicted by plausible collapse models. This effect cannot account directly for the variation of velocity dispersion with age observed for stars younger than 10 yr, but Tinsley & Larson suggested that this could be explained if the velocity dispersion of the youngest stars reflects only the local turbulent motions of the gas, while the velocity dispersion of older stars reflects in addition larger-scale non-circular motions in the galactic gas layer. If the interstellar medium possesses a hierarchy of motions whose velocity dispersion increases with the size of the region considered, older stars which have traveled farther since their formation will sample the gas motions over a larger volume of space, and thus will have a larger velocity dispersion than the younger stars.