标题： 宇宙射线驱动的外流对宇宙学模拟中Lyman-$α$发射的影响 显示英文标题

标题： Impact of Cosmic Ray-driven Outflows on Lyman-$α$ Emission in Cosmological Simulations

摘要： 宇宙射线（CR）反馈被认为是一种强大的机制，可以驱动星系中的温暖气体外流。 我们使用宇宙学磁流体动力学模拟来研究CR反馈对一个$10^{11}\,M_\odot$暗物质晕在$2<z<4$时的中性氢（HI）的影响。 为此，我们用电离辐射转移对模拟进行后处理，并执行蒙特卡罗莱曼-$\alpha$（Lya）转移计算。 CR反馈降低了年轻恒星周围的HI柱密度，从而允许更多的Lya光子逃逸，进而更好地匹配观测到的Lya发射体的Lya光度。 尽管具有CR驱动外流的星系在星系际介质中有更多的扩展HI，但两个对光学深度和气体运动敏感的Lya线特性——速度空间中红峰的位置（$v_\mathrm{red}$）以及蓝峰与红峰的相对强度（$B/R$）——无法区分CR驱动和非CR模拟。 这是因为Lya光子优先沿着电离辐射产生的低HI密度通道传播，从而限制了与体积填充HI的散射。 相反，观测到的谷值和峰值之间的低通量比以及表面亮度分布在具有CR驱动外流的模型中得到了更好的再现，因为Lya光子在逃逸前发生了更多相互作用，而不是像非CR模拟中那样被尘埃破坏。 我们讨论了在表现出明显红峰和大$v_\mathrm{red}$的模拟中视线数量稀少的潜在原因，这可能需要存在更多的体积填充HI。 显示英文摘要

摘要： Cosmic ray (CR) feedback has been proposed as a powerful mechanism for driving warm gas outflows in galaxies. We use cosmological magnetohydrodynamic simulations to investigate the impact of CR feedback on neutral hydrogen (HI) in a $10^{11}\,M_\odot$ dark matter halo at $2<z<4$. To this end, we post-process the simulations with ionizing radiative transfer and perform Monte Carlo Lyman-$\alpha$ (Lya) transfer calculations. CR feedback reduces HI column densities around young stars, thereby allowing more Lya photons to escape and consequently offering a better match to the Lya luminosities of observed Lya emitters. Although galaxies with CR-driven outflows have more extended HI in the circumgalactic medium, two Lya line properties sensitive to optical depth and gas kinematics - the location of the red peak in velocity space ($v_\mathrm{red}$) and relative strength of the blue-to-red peaks ($B/R$) - cannot distinguish between the CR-driven and non-CR simulations. This is because Lya photons propagate preferentially along low HI density channels created by the ionizing radiation, thereby limiting the scattering with volume-filling HI. In contrast, the observed low flux ratios between the valley and peak and the surface brightness profiles are better reproduced in the model with CR-driven outflows because the Lya photons interact more before escaping, rather than being destroyed by dust as is the case in the non-CR simulation. We discuss the potential cause of the paucity of sightlines in simulations that exhibit prominent red peaks and large $v_\mathrm{red}$, which may require the presence of more volume-filling HI.