Early results from the JWST observations have reported a surprisingly high number of UV-bright galaxies at z ≥ 10, which appears to challenge the theoretical predictions from standard galaxy formation models in the ΛCDM framework at these redshifts. To alleviate this tension, several cosmological and astrophysical interpretations have been advanced. However, all of these proposed scenarios carry noteworthy consequences for other large-scale processes in the early Universe, particularly cosmic reionization, since high-redshift galaxies are believed to be the primary ionizing sources during the Epoch of Reionization (EoR). To investigate this, we introduce a semi-analytical model of galaxy formation and evolution that explains the evolving galaxy UV luminosity function (UVLF) over 6 ≲ z ≲ 15, and also jointly tracks the time evolution of the globally averaged neutral hydrogen fraction in the intergalactic medium. The model self-consistently accounts for the suppression of star formation in low-mass galaxies due to reionization feedback and is constrained by comparing the model predictions with various observational probes like the UVLF data from HST and JWST, recent measurements of the neutral hydrogen fraction, and the CMB scattering optical depth. Our analysis confirms that a rapid enhancement in the star-formation rate efficiency and/or UV luminosity per stellar mass formed is necessary for consistency with the JWST UVLF estimates at z ≥ 10. We further find that it is possible to jointly satisfy the current reionization constraints when the escape fraction is assumed to be halo-mass dependent, requiring higher Lyman-continuum leakage from low-mass galaxies. We also examine the relative contribution of galaxies with different UV luminosities towards the ionizing photon budget for the EoR and investigate the large-scale bias of high-z galaxies.

中文翻译：

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模拟高红移星系的恒星形成活动和电离特性


JWST 观测的早期结果报告称，在z ≥ 10，这似乎挑战了 ΛCDM 框架中标准星系形成模型对这些红移的理论预测。为了缓解这种紧张，人们提出了几种宇宙学和天体物理学的解释。然而，所有这些提出的场景都对早期宇宙的其他大规模过程产生了值得注意的影响，特别是宇宙再电离，因为高红移星系被认为是再电离时代（EoR）期间的主要电离源。为了研究这一点，我们引入了星系形成和演化的半解析模型，该模型解释了演化中的星系紫外光度函数（UVLF）超过 6 ≲ z ≲ 15，并且还共同跟踪了星际介质中全球平均中性氢分数的时间演化。该模型自洽地解释了由于再电离反馈而导致低质量星系中恒星形成的抑制，并通过将模型预测与各种观测探测器（例如来自 HST 和 JWST 的 UVLF 数据、最近对中性氢分数的测量、和 CMB 散射光学深度。我们的分析证实，为了与 JWST UVLF 估计值保持一致，恒星形成率效率和/或每形成恒星质量的紫外光度的快速提高是必要的。 z ≥ 10。我们进一步发现，当假设逃逸分数与晕质量相关时，可以共同满足当前的再电离约束，需要来自低质量星系的更高的莱曼连续谱泄漏。 我们还研究了具有不同紫外光度的星系对 EoR 电离光子预算的相对贡献，并研究了高尺度偏差z星系。