标题： 原始恒星云的演化 --- 准静态分析 --- 显示英文标题

标题： Evolution of Primordial Protostellar Clouds --- Quasi-Static Analysis ---

摘要： 研究了具有恒星质量的无金属分子云（或云核）的收缩过程。 我们计算了H₂线的辐射转移，并检查了具有辐射冷却的准静态收缩。 通过比较这些核心的自由下落时间t_ff和准静态收缩时间尺度t_qsc（接近冷却时间t_cool）发现，即使在存在冷且不透明包层的情况下，这两个时间尺度之比t_ff/t_qsc（即冷却效率）随着收缩而增大。 特别是对于原始丝状云的碎片，在碎裂时期t_ff近似等于t_qsc时，它们以自由下落时间尺度动态塌缩。 这种冷却效率仅适用于线冷却。 显示英文摘要

摘要： The contraction processes of metal-free molecular clouds of starlike mass (or cloud cores) are investigated. We calculate radiative transfer of the H_2 lines and examine quasi-static contraction with radiative cooling. Comparing two time-scales, the free-fall time t_ff and the time-scale of quasi-static contraction t_qsc (nearly equal to t_cool, the cooling time) of these cores, we find that the ratio of the two time-scales t_ff/t_qsc, i.e., the efficiency of cooling, becomes larger with contraction even under the existence of cold and opaque envelopes. In particular, for fragments of primordial filamentary clouds, for which t_ff is nearly equal to t_qsc at the fragmentation epoch, they collapse dynamically in the free-fall time-scale. This efficiency of cooling is unique to line cooling.