arXiv 2207.032322022-07-07astro-ph.GA

再电离时期SPHINX星系的LyC逃逸

LyC escape from SPHINX galaxies in the Epoch of Reionization

Joakim Rosdahl, Jérémy Blaizot, Harley Katz, Taysun Kimm, Thibault Garel, Martin Haehnelt, Laura C. Keating, Sergion Martin-Alvarez, Léo Michel-Dansac, Pierre Ocvirk

备注：: 20 figures, 21 pages plus appendices. Accepted for publication in MNRAS
DOI：: 10.1093/mnras/stac1942

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摘要：

我们测量逃逸分数，$f_{\rm esc}$，电离辐射从星系中的SPHINX宇宙辐射流体动力学模拟的再电离，解决晕与$M_{\rm vir} \gtrapprox 7.5 \times 10^7 \ M_{\odot}$的最小细胞宽度为$\approx 10$ pc。我们的新的和最大的$20$共同移动的Mpc宽体积包含数以万计的恒星形成星系的晕质量高达几倍$10^{11} \ M_{\odot}$。模拟的星系符合再电离时期紫外光度函数的观测约束。由于超新星和辐射反馈的调节，逃逸分数在几个百万年的时间尺度内在单个星系中强烈波动，并且在任何给定的时间，一小部分恒星形成星系发出大部分逃逸到星系间介质中的电离辐射。从统计学上看，$f_{\rm esc}$在中等质量、中等亮度和低金属含量的星系（$M_{*} \approx 10^7 \ M_{\odot}$、$M_{1500} \approx -17$、$Z\lesssim 5 \times 10^{-3} \ Z_{\odot}$）中达到峰值，在质量较低和较高、较亮和较暗的星系以及金属含量较高的星系中强烈下降。逃逸分数与短期和长期的特定恒星形成率呈正相关。根据SPHINX，星系太暗，尚未观察到，与$M_{1500} \gtrapprox -17$，提供约$55$百分比的光子有助于再电离。全球平均的$f_{\rm esc}$自然地随着红移的减小而减小，正如紫外背景模型和低红移观测所预测的那样。这种演化是由宇宙时间内特定恒星形成率的下降所驱动的。

英文摘要：

We measure escape fractions, $f_{\rm esc}$, of ionizing radiation from galaxies in the SPHINX suite of cosmological radiation-hydrodynamical simulations of reionization, resolving halos with $M_{\rm vir} \gtrapprox 7.5 \times 10^7 \ M_{\odot}$ with a minimum cell width of $\approx 10$ pc. Our new and largest $20$ co-moving Mpc wide volume contains tens of thousands of star-forming galaxies with halo masses up to a few times $10^{11} \ M_{\odot}$. The simulated galaxies agree well with observational constraints of the UV luminosity function in the Epoch of Reionization. The escape fraction fluctuates strongly in individual galaxies over timescales of a few Myrs, due to its regulation by supernova and radiation feedback, and at any given time a tiny fraction of star-forming galaxies emits a large fraction of the ionizing radiation escaping into the inter-galactic medium. Statistically, $f_{\rm esc}$ peaks in intermediate-mass, intermediate-brightness, and low-metallicity galaxies ($M_{*} \approx 10^7 \ M_{\odot}$, $M_{1500} \approx -17$, $Z\lesssim 5 \times 10^{-3} \ Z_{\odot}$), dropping strongly for lower and higher masses, brighter and dimmer galaxies, and more metal-rich galaxies. The escape fraction correlates positively with both the short-term and long-term specific star formation rate. According to SPHINX, galaxies too dim to be yet observed, with $M_{1500} \gtrapprox -17$, provide about $55$ percent of the photons contributing to reionization. The global averaged $f_{\rm esc}$ naturally decreases with decreasing redshift, as predicted by UV background models and low-redshift observations. This evolution is driven by decreasing specific star formation rates over cosmic time.

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