标题： 未解析湍流对电离连续谱光子逃逸比例的影响 显示英文标题

标题： The Impact of Unresolved Turbulence on the Escape Fraction of Lyman Continuum Photons

摘要： 我们研究高红移星系中湍流马赫数（\mach ）与莱曼连续谱光子逃逸分数（$f_{\rm esc}$）之间的关系。 将湍流近似为等温且各向同性，我们表明从$\mathcal{M}=1$到$\mathcal{M}=10$的柱密度方差增加导致$f_{\rm esc}$增加了$\approx 25$%，而从$\mathcal{M}=1$到$\mathcal{M}=20$的增加导致对于消光为$\tau\approx1$的介质，$f_{\rm esc}$增加了$\approx 50$%。 在固定马赫数下，相对于恒定柱密度情况的逃逸分数校正因子随单元的不透明度呈指数变化，这对模拟的恒星形成区域有重大影响。 此外，在包含完整原子/离子冷却和化学过程的各向同性湍流模拟中，HI的比例在$\mathcal{M}\approx10$时下降了$\approx 2.5$倍，即使平均温度是$\approx5\times10^3 K$。 如果湍流未被解析，这些效应共同使$f_{\rm esc}$在马赫数高于10时增加$>3$倍。 这样的马赫数在高红移处很常见，强烈的湍流由超新星、引力不稳定性和合并活动驱动，这既通过数值模拟也通过观测得到了证明。 如果将这些结果纳入当前的流体动力学宇宙学模拟以考虑未解析的湍流，可以提高莱曼连续谱光子逃逸分数的理论预测，并进一步限制再电离的来源。 显示英文摘要

摘要： We investigate the relation between the turbulent Mach number (\mach) and the escape fraction of Lyman continuum photons ($f_{\rm esc}$) in high-redshift galaxies. Approximating the turbulence as isothermal and isotropic, we show that the increase in the variance in column densities from $\mathcal{M}=1$ to $\mathcal{M}=10$ causes $f_{\rm esc}$ to increase by $\approx 25$\%, and the increase from $\mathcal{M}=1$ to $\mathcal{M}=20$ causes $f_{\rm esc}$ to increases by $\approx 50$\% for a medium with opacity $\tau\approx1$. At a fixed Mach number, the correction factor for escape fraction relative to a constant column density case scales exponentially with the opacity in the cell, which has a large impact for simulated star forming regions. Furthermore, in simulations of isotropic turbulence with full atomic/ionic cooling and chemistry, the fraction of HI drops by a factor of $\approx 2.5$ at $\mathcal{M}\approx10$ even when the mean temperature is $\approx5\times10^3 K$. If turbulence is unresolved, these effects together enhance $f_{\rm esc}$ by a factor $>3$ at Mach numbers above 10. Such Mach numbers are common at high-redshifts where vigorous turbulence is driven by supernovae, gravitational instabilities, and merger activity, as shown both by numerical simulations and observations. These results, if implemented in the current hydrodynamical cosmological simulations to account for unresolved turbulence, can boost the theoretical predictions of the Lyman Continuum photon escape fraction and further constrain the sources of reionization.