实施尘埃屏蔽作为恒星形成的标准
Implementing Dust Shielding as a Criteria for Star Formation
摘要：
恒星的形成被观察到与分子气体的密集区域密切相关。虽然恒星形成和分子氢之间联系的确切性质仍然不清楚，但有些人认为尘埃颗粒对致密气体的屏蔽是使两者存在的关键因素。我们提出了一个用于星系形成模拟的子网格模型，其中恒星的形成是明确地联系到当地的尘埃屏蔽。我们开发和测试我们的屏蔽和恒星形成模型，使用平滑粒子流体动力学模拟太阳和太阳下的金属孤立的银河系质量盘星系。我们比较了我们的尘埃屏蔽为基础的恒星形成模型的其他两个恒星形成配方，使用气体温度和H $_2$分数作为恒星形成的标准。我们进一步遵循的宇宙学背景下，使用屏蔽和H $_2$为基础的恒星形成模型的矮星系的演化。我们发现，屏蔽为基础的模型允许在更高的温度和更低的密度比一个模型，在该模型中，恒星的形成是直接绑定到H $_2$丰度，因为需要H $_2$形成导致气体进行额外的引力坍缩恒星形成之前。然而，所得到的星系是非常相似的屏蔽和H $_2$为基础的恒星形成模型，两个模型再现解决肯尼卡特-施密特定律。因此，这两种恒星形成模型在星系形成模拟中似乎都是可行的。
英文摘要：
Star formation is observed to be strongly correlated to dense regions of molecular gas. Although the exact nature of the link between star formation and molecular hydrogen is still unclear, some have suggested that shielding of dense gas by dust grains is the key factor enabling the presence of both. We present a sub-grid model for use in galaxy formation simulations in which star formation is linked explicitly to local dust shielding. We developed and tested our shielding and star formation models using smoothed particle hydrodynamic simulations of solar and sub-solar metallicity isolated Milky Way-mass disk galaxies. We compared our dust shielding-based star formation model to two other star formation recipes that used gas temperature and H$_2$ fraction as star formation criteria. We further followed the evolution of a dwarf galaxy within a cosmological context using both the shielding and H$_2$-based star formation models. We find that the shielding-based model allows for star formation at higher temperatures and lower densities than a model in which star formation is tied directly to H$_2$ abundance, as requiring H$_2$ formation leads the gas to undergo additional gravitational collapse before star formation. However, the resulting galaxies are very similar for both the shielding and H$_2$-based star formation models, and both models reproduce the resolved Kennicutt-Schmidt law. Therefore, both star formation models appear viable in the context of galaxy formation simulations.
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