标题： 关于恒星形成历史和诞生线的推断的评论 显示英文标题

标题： Comments on Inferences of Star Formation Histories and Birthlines

摘要： 帕拉和斯塔勒最近提出，在御夫座和其他附近的分子云中的恒星形成过程持续至少10百万年，这意味着分子云的演化和恒星形成几乎是静态的。他们的结论与近期其他研究结果相矛盾，后者表明分子云是短暂存在的天体，而恒星形成过程则迅速进行。 帕拉和斯塔勒的观点暗示大多数分子云应该具有极低的恒星形成率，并且在这些不活跃阶段，恒星初始质量函数应明显偏向于产生质量为$\gtrsim 1 \msun$的恒星；然而，这两种预测均未得到观测的支持。 我指出，帕拉和斯塔勒关于御夫座的结论几乎完全依赖于少数质量为$\gtrsim 1 \msun$的恒星；较低质量的恒星并未显示出如此长时间的恒星形成期的证据。 我还进一步证明，在御夫座方向上看起来比10百万年更老的大多数恒星很可能位于前景且并非成员。 此外，我还展示了“出生线”计算，支持这样一种观点：质量为$\gtrsim 1 \msun$的恒星年龄可能被系统性地高估了，因为“出生线”年龄校正被低估了；这种出生线可以消除假设初始质量函数偏斜的必要性。 目前观测到的大多数年轻恒星最简单且最可靠的解释是，分子云和恒星形成过程是快速且动态的。 显示英文摘要

摘要： Palla & Stahler have recently argued that star formation in Taurus and other nearby molecular clouds extends over a period of at least 10 Myr, implying quasi-static cloud evolution and star formation. Their conclusions contradict other recent results indicating that molecular clouds are transient objects and star formation proceeds rapidly. The Palla & Stahler picture implies that most molecular clouds should have extremely low rates of star formation, and that in such inactive stages the stellar initial mass function should be strongly skewed toward producing stars with masses $\gtrsim 1 \msun$; neither prediction is supported by observations. I show that the Palla & Stahler conclusions for Taurus depend almost entirely on a small number of stars with masses $\gtrsim 1 \msun$; the lower-mass stars show no evidence for such an extended period of star formation. I further show that most of the stars apparently older than 10 Myr in the direction of Taurus are probably foreground non-members. I also present birthline calculations which support the idea that the ages of the stars with masses $\gtrsim 1 \msun$ have been systematically overestimated because ``birthline'' age corrections have been underestimated; such birthlines would eliminate the need to postulate skewed initial mass functions. The simplest and most robust explanation of current observations characterizing the vast majority of young stars in molecular clouds is that cloud and star formation is rapid and dynamic.