arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1105.4777astro-ph.GA
收藏

坍缩分子云及其恒星形成活动的演化模型

An Evolutionary Model for Collapsing Molecular Clouds and Their Star Formation Activity

Manuel Zamora-Aviles, Enrique Vázquez-Semadeni, Pedro Colín

摘要:

我们提出了一个理想化的,半经验模型的引力收缩分子云(MC)的演变和他们的恒星形成率(SFR)和效率(SFE)。该模型假设瞬时SFR由高于一定密度阈值的质量除以其自由落体时间给出。大质量恒星的瞬时数量是在假设Kroupa IMF的情况下计算的。这些恒星通过电离辐射对星云进行反馈,侵蚀星云,而星云演化的主要控制参数是星云的最大质量$\Mmax$。这使我们能够将模型云的各种属性与观测对应物进行比较。巨分子云(GMC)模型($\Mmax \sim 10^5 \Msun$)非常符合Kawamura等人(2009)最近推断的大麦云云中GMC的演化情景。在肯尼库特-施密特图中,一个具有$\Mmax \approx 2000 \Msun$的模型云首先经过典型的低到中等质量恒星形成云的轨迹,然后在$\sim 10$ Myr的过程中向高质量恒星形成云的轨迹移动。此外,恒星年龄直方图为这个云的几个万年前,它的破坏同意非常好的观察到的$ρ$ -Oph恒星协会,其母云有一个类似的质量,并意味着SFR的云随时间而增加。因此,我们的模型与观测到的恒星形成MC的各种性质一致,这表明引力坍缩MC的情况,其SFR由恒星反馈调节,是完全可行的,并与分子云的关键观测性质一致。

英文摘要:

We present an idealized, semi-empirical model for the evolution of gravitationally contracting molecular clouds (MCs) and their star formation rate (SFR) and efficiency (SFE). The model assumes that the instantaneous SFR is given by the mass above a certain density threshold divided by its free-fall time. The instantaneous number of massive stars is computed assuming a Kroupa IMF. These stars feed back on the cloud through ionizing radiation, eroding it. The main controlling parameter of the evolution turns out to be the maximum cloud mass, $\Mmax$. This allows us to compare various properties of the model clouds against their observational counterparts. A giant molecular cloud (GMC) model ($\Mmax \sim 10^5 \Msun$) adheres very well to the evolutionary scenario recently inferred by Kawamura et al. (2009) for GMCs in the Large Magellanic Cloud. A model cloud with $\Mmax \approx 2000 \Msun$ evolves in the Kennicutt-Schmidt diagram first passing through the locus of typical low- to-intermediate mass star-forming clouds, and then moving towards the locus of high-mass star-forming ones over the course of $\sim 10$ Myr. Also, the stellar age histograms for this cloud a few Myr before its destruction agree very well with those observed in the $ρ$-Oph stellar association, whose parent cloud has a similar mass, and imply that the SFR of the clouds increases with time. Our model thus agrees well with various observed properties of star-forming MCs, suggesting that the scenario of gravitationally collapsing MCs, with their SFR regulated by stellar feedback, is entirely feasible and in agreement with key observed properties of molecular 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。

↑