论文标题
在银河系质量星系的宇宙学模拟中重现Co-to-H $ _2 $转换因子
Reproducing the CO-to-H$_2$ conversion factor in cosmological simulations of Milky Way-mass galaxies
论文作者
论文摘要
我们介绍了在Fire-2宇宙缩放模拟中，在红移零的银河系质量星系中，CO（1-0）发射的模型。我们通过在考虑局部来源的效果的同时使用平衡化学求解器进行后处理来计算分子丰度，并使用线辐射传输代码确定新兴CO（1-0）排放。我们发现结果在很大程度上取决于假定的屏蔽长度，在我们的模型中，该长度设置了入射UV辐射场的衰减。在这些模拟的分辨率下，屏蔽长度的常用选择（例如牛仔裤长度）导致在给定的h $ _2 $丰度下过高的co丰度。 We find that a model with a distribution of shielding lengths, which has a median shielding length of $\sim 3$ pc in cold gas ($T < 300$ K) for both CO and H$_{2}$, is able to reproduce both the observed CO(1-0) luminosity and inferred CO-to-H$_{2}$ conversion factor at a given star formation rate compared with observations.我们建议可以将这种短的屏蔽长度视为一个子网格模型，该模型控制着穿透巨大分子云的辐射量。
We present models of CO(1-0) emission from Milky Way-mass galaxies at redshift zero in the FIRE-2 cosmological zoom-in simulations. We calculate the molecular abundances by post-processing the simulations with an equilibrium chemistry solver while accounting for the effects of local sources, and determine the emergent CO(1-0) emission using a line radiative transfer code. We find that the results depend strongly on the shielding length assumed, which in our models sets the attenuation of the incident UV radiation field. At the resolution of these simulations, commonly used choices for the shielding length, such as the Jeans length, result in CO abundances that are too high at a given H$_2$ abundance. We find that a model with a distribution of shielding lengths, which has a median shielding length of $\sim 3$ pc in cold gas ($T < 300$ K) for both CO and H$_{2}$, is able to reproduce both the observed CO(1-0) luminosity and inferred CO-to-H$_{2}$ conversion factor at a given star formation rate compared with observations. We suggest that this short shielding length can be thought of as a subgrid model which controls the amount of radiation that penetrates giant molecular clouds.
