快速恒星形成与全球引力坍缩
Rapid Star Formation and Global Gravitational Collapse
摘要：
在附近的分子云中，大多数年轻恒星的年龄估计在1-2百万年之间，这表明恒星的形成是迅速的。然而，在这些区域中有少数恒星的年龄在5- 1000万年之间，这被认为是恒星形成的一个缓慢的准静态过程。当考虑这些不同的图像时，重要的是要认识到，在一个给定的恒星形成云中的年龄分布必然是局部坍缩时间尺度的上限，因为不是所有空间上不同的区域都将在同一时刻开始收缩。此外，恒星形成云可能在几百万年的时间尺度上动态演化;特别是，由于局部气体密度普遍增加，全球引力收缩将倾向于产生随时间增加的恒星形成率。我们表明，两种不同的数值模拟的动态，流动驱动的分子云的形成和演化1）预测年龄传播的主要恒星星族大致与观察一致，和2）提高形成少量的恒星的可能性在云的早期演化，全球收缩之前集中的气体和大部分的恒星星族的生产。一般来说，在一个年轻得多的群体中存在少量较老的恒星与动态恒星形成的图像是一致的，甚至可能提供恒星形成云的时间演化的线索。
英文摘要：
Most young stars in nearby molecular clouds have estimated ages of 1-2 Myr, suggesting that star formation is rapid. However, small numbers of stars in these regions with inferred ages of >= 5-10 Myr have been cited to argue that star formation is instead a slow, quasi-static process. When considering these alternative pictures it is important to recognize that the age spread in a given star-forming cloud is necessarily an upper limit to the timescales of local collapse, as not all spatially-distinct regions will start contracting at precisely the same instant. Moreover, star-forming clouds may dynamically evolve on timescales of a few Myr; in particular, global gravitational contraction will tend to yield increasing star formation rates with time due to generally increasing local gas densities. We show that two different numerical simulations of dynamic, flow-driven molecular cloud formation and evolution 1) predict age spreads for the main stellar population roughly consistent with observations, and 2) raise the possibility of forming small numbers of stars early in cloud evolution, before global contraction concentrates the gas and the bulk of the stellar population is produced. In general, the existence of a small number of older stars among a generally much-younger population is consistent with the picture of dynamic star formation, and may even provide clues to the time evolution of star-forming clouds.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
