Incorporating the Molecular Gas Phase in Galaxy-sized Numerical Simulations: First Applications in Dwarf Galaxies
Incorporating the Molecular Gas Phase in Galaxy-sized Numerical Simulations: First Applications in Dwarf Galaxies
复制标题
将分子气相纳入星系大小的数值模拟：在矮星系中的首次应用
DOI：
10.1086/504366
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发表时间：
2006
期刊：
影响因子：
--
通讯作者：
P. P. van der Werf
中科院分区：
文献类型：
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作者：
F. I. Pelupessy;P. Papadopoulos;P. P. van der Werf
我们提出了星系中气体和恒星含量耦合演化的模型，其中包括氢气体中H2的形成。为此，我们建立了气体云的子网格模型，该模型利用观测到的云尺度关系，跟踪了尘埃颗粒上H2的形成及其在CNM阶段被紫外线照射的破坏，包括尘埃和H2自屏蔽的屏蔽效应，以及它在WNM阶段的碰撞破坏。然后，我们将我们的模型应用于一个典型的静止矮星系的演化。除了它们在星系演化中的重要性外，它们的小尺寸使我们的模拟能够跟踪密度为n ~ 100 cm-3，冷至Tk ~ 40 K的气体的热演化和动态演化，其中大部分H→H2转变（和恒星形成）发生。我们的发现包括：(1)产生的H2气体质量强烈依赖于环境金属丰度和采用的H2形成速率，(2)恒星反馈对H2形成的影响对恒星形成参数的限制，以及(3)恒星形成区域外弥漫H2气相的可能性。我们期望这些结果在其他类型的星系中也是有效的，因为H→H2相变很难通过高分辨率的数值研究来解决（例如，大螺旋）。最后，我们简要地研究了H2分数阈值作为一种新的、更现实的恒星形成标准，用于星系模拟。
We present models of the coupled evolution of the gaseous and stellar content of galaxies incorporating the formation of H2 out of H gas. We do so by formulating a subgrid model for gas clouds that uses observed cloud scaling relations and tracks the formation of H2 on dust grains and its destruction by UV irradiation in the CNM phase, including the effects of shielding by dust and H2 self-shielding, as well as its collisional destruction in the WNM phase. We then apply our model to the evolution of a typical quiescent dwarf galaxy. Apart from their importance in galaxy evolution, their small size allows our simulations to track the thermal and dynamic evolution of gas as dense as n ~ 100 cm-3 and as cold as Tk ~ 40 K, where most of the H → H2 transition (and star formation) takes place. Our findings include (1) a strong dependence of the resulting H2 gas mass on the ambient metallicity and the adopted H2 formation rate, (2) constraints on the star formation parameters from the effects of stellar feedback on H2 formation, and (3) the possibility of a diffuse H2 gas phase outside star-forming regions. We expect these results to be valid in other types of galaxies for which the H → H2 phase transition is more difficult to resolve by high-resolution numerical studies (e.g., large spirals). Finally, we briefly examine using an H2 fraction threshold as a new, more realistic, star formation criterion for use in galaxy simulations.