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arXiv 0903.4098astro-ph.GA
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恒星形成与表面密度关系的一个简单模型

A Simple Model for the Relationship Between Star Formation and Surface Density

C. L. Dobbs, J. E. Pringle

摘要:

我们研究了单位面积恒星形成率与ISM表面密度之间的关系(局部Kennicutt-Schmitt定律)使用ISM的简化模型和基于束缚团块中气体质量的恒星形成率的简单估计,团块的局部动力学时标,以及约5%的效率参数。尽管方法简单,我们能够再现恒星形成率和致密(分子)气体表面密度之间的观测线性关系。我们使用一个简单的模型的H_2分数依赖于总面密度来论证为什么总面密度和HI面密度都不是恒星形成率的良好的本地指标。我们还调查的螺旋势的深度上的恒星形成率的依赖关系。我们的模型表明,平均恒星形成率并不显着依赖于螺旋势的强度,但更强的螺旋势,对于给定的平均表面密度,确实会导致更多的恒星形成发生在靠近螺旋臂。这与观测结果一致,即与絮状星系相比,宏伟设计星系似乎没有显示出更大程度的恒星形成。

英文摘要:

We investigate the relationship between the star formation rate per unit area and the surface density of the ISM (the local Kennicutt-Schmitt law) using a simplified model of the ISM and a simple estimate of the star formation rate based on the mass of gas in bound clumps, the local dynamical timescales of the clumps, and an efficiency parameter of around 5 per cent. Despite the simplicity of the approach, we are able to reproduce the observed linear relation between star formation rate and surface density of dense (molecular) gas. We use a simple model for the dependence of H_2 fraction on total surface density to argue why neither total surface density nor the HI surface density are good local indicators of star formation rate. We also investigate the dependence of the star formation rate on the depth of the spiral potential. Our model indicates that the mean star formation rate does not depend significantly on the strength of the spiral potential, but that a stronger spiral potential, for a given mean surface density, does result in more of the star formation occurring close to the spiral arms. This agrees with the observation that grand design galaxies do not appear to show a larger degree of star formation compared to their flocculent counterparts.

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