论文标题
没有缺少电源的光子：来自Fire-2模拟的中等电离光子逃生部分
No missing photons for reionization: moderate ionizing photon escape fractions from the FIRE-2 simulations
论文作者
论文摘要
我们从现实环境项目中的反馈中，在34个高分辨率的宇宙缩放模拟的样品中介绍了34个高分辨率宇宙缩放模拟的氢气电离光子（F_ESC）的逃逸分数，该样品是在现实环境项目中的Z> 5样本，并通过蒙特卡洛辐射传输代码进行了后处理，用于电离辐射。我们的样本由M_VIR 〜10^8--10^{12} m_sun（m_star〜10^4--10^{10} m_sun）中的8500 Halos组成，z = 5--12。我们发现样品平均<f_esc>随着m_vir〜10^8--10^{9.5} m_sun的晕质量增加，对于m_vir〜10^{9.5} -10^{11} m_sun而言，m_vir〜10^{9.5} m_sun几乎变为恒定，并且在m_vir> 10^{11} m_sun中减少。等效地，<f_esc>随着恒星质量的增加而增加至m_star 〜10^8 m_sun，并在较高的质量下减小。即使应用单星恒星种群合成模型，我们在M_star〜10^8 m_sun处的星系中发现了一个中等<F_ESC> 〜0.2。逃脱的电离光子中有将近一半来自1--3的星星，其余的来自3--10 Myr的星星。二进制文件仅具有适度的效果，将<F_ESC>提高〜25--35％，而逃逸光子的数量增加了60--80％。大多数泄漏的电离光子来自急剧形成的恒星形成区域，这些区域通常包含反馈驱动的KPC规模的超级气泡，被密集的外壳包围。壳在加速的同时形成恒星，因此在外壳中以前形成的新恒星已经在外壳内部。气泡中的年轻恒星和壳的边缘附近可以完全电离通过反馈预先清除的一些低柱密度路径，从而使其电离光子的很大一部分逸出。在高质量端处的<f_esc>的减少是由于尘埃衰减所致，而在低质量端，<f_esc>由于效率低下的恒星形成（因此反馈）而降低。在固定质量下，<f_esc>倾向于随着红移而增加。我们的模拟产生了足够的电离光子来进行宇宙电离。
We present the escape fraction of hydrogen ionizing photons (f_esc) from a sample of 34 high-resolution cosmological zoom-in simulations of galaxies at z>5 in the Feedback in Realistic Environments project, post-processed with a Monte Carlo radiative transfer code for ionizing radiation. Our sample consists of 8500 halos in M_vir~10^8--10^{12} M_sun (M_star~10^4--10^{10} M_sun) at z=5--12. We find the sample average <f_esc> increases with halo mass for M_vir~10^8--10^{9.5} M_sun, becomes nearly constant for M_vir~10^{9.5}--10^{11} M_sun, and decreases at M_vir>10^{11} M_sun. Equivalently, <f_esc> increases with stellar mass up to M_star~10^8 M_sun and decreases at higher masses. Even applying single-star stellar population synthesis models, we find a moderate <f_esc>~0.2 for galaxies at M_star~10^8 M_sun. Nearly half of the escaped ionizing photons come from stars 1--3 Myr old and the rest from stars 3--10 Myr old. Binaries only have a modest effect, boosting <f_esc> by ~25--35% and the number of escaped photons by 60--80%. Most leaked ionizing photons are from vigorously star-forming regions that usually contain a feedback-driven kpc-scale superbubble surrounded by a dense shell. The shell is forming stars while accelerated, so new stars formed earlier in the shell are already inside the shell. Young stars in the bubble and near the edge of the shell can fully ionize some low-column-density paths pre-cleared by feedback, allowing a large fraction of their ionizing photons to escape. The decrease of <f_esc> at the high-mass end is due to dust attenuation, while at the low-mass end, <f_esc> decreases owing to inefficient star formation (and hence feedback). At fixed mass, <f_esc> tends to increase with redshift. Our simulations produce sufficient ionizing photons for cosmic reionization.
