来自二进制演化的延迟光子帮助宇宙重新电离
Delayed Photons from Binary Evolution Help Reionize the Universe
摘要：
包含反馈的高分辨率数值模拟旨在计算氢电离光子的逃逸分数（fesc），通常假设恒星辐射基于单恒星星族合成模型。然而，强有力的证据表明大质量恒星的双星比例是70%。此外，到目前为止，模拟得出的fesc值仅落在大约10-20%范围的低端，这是假设宇宙膨胀所必需的量。通过分析高分辨率（4 pc）宇宙辐射流体动力学模拟，我们研究了当我们包含两种不同的双星恒星演化产物--剥离氢包层的恒星和大质量蓝离散星时fesc的变化。两者在每次星暴后都会产生大量的电离光子，约为10-200百万r。我们发现这些光子的相对重要性相对于逃逸的电离光子被放大，因为恒星形成率（SFR）和fesc的峰值通常在这10-200百万年之间不同步。此外，低质量，爆发星系发射莱曼连续辐射主要来自二进制产品时，SFRs低。詹姆斯·韦伯太空望远镜对这些星系的观测可以提供关于双星演化作为红移函数的关键信息。总的来说，包括剥离星和大质量蓝离散星，我们的光子加权平均逃逸分数分别增加了约13%和10%，导致平均fesc为17%。我们的结果强调，使用更新的恒星星族合成模型与二进制恒星演化提供了一个更健全的物理基础，恒星再电离。
英文摘要：
High-resolution numerical simulations including feedback and aimed at calculating the escape fraction (fesc) of hydrogen-ionizing photons often assume stellar radiation based on single-stellar population synthesis models. However, strong evidence suggests the binary fraction of massive stars is 70%. Moreover, simulations so far yield values of fesc falling only on the lower end of the roughly 10-20% range, the amount presumed necessary to reionize the Universe. Analyzing a high-resolution (4 pc) cosmological radiation hydrodynamic simulation we study how fesc changes when we include two different products of binary stellar evolution - stars stripped of their hydrogen envelopes and massive blue stragglers. Both produce significant amounts of ionizing photons 10-200 Myr after each starburst. We find the relative importance of these photons are amplified with respect to escaped ionizing photons, because peaks in star formation rates (SFRs) and fesc are often out of phase by this 10-200 Myr. Additionally, low mass, bursty galaxies emit Lyman continuum radiation primarily from binary products when SFRs are low. Observations of these galaxies by the James Webb Space Telescope could provide crucial information on the evolution of binary stars as a function of redshift. Overall, including stripped stars and massive blue stragglers increases our photon-weighted mean escape fraction by around 13% and 10%, respectively, resulting in a mean fesc of 17%. Our results emphasize that using updated stellar population synthesis models with binary stellar evolution provides a more sound physical basis for stellar reionization.
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