The James Webb Space Telescope (JWST) will revolutionize our understanding of early galaxy formation, and could potentially set stringent constraints on the nature of dark matter. We use a semi-empirical model of galaxy formation to investigate the extent to which uncertainties in the implementation of baryonic physics may be degenerate with the predictions of two different models of dark matter – cold dark matter (CDM) and a 7 keV sterile neutrino, which behaves as warm dark matter (WDM). Our models are calibrated to the observed UV luminosity function at z = 4 using two separate dust attenuation prescriptions, which manifest as high and low star formation efficiency in low-mass haloes. These efficiencies capture the net effect of processes that regulate star formation. We find that while at fixed star formation efficiency, ε, there are marked differences in the abundance of faint galaxies in the two dark matter models at high-z; these differences are mimicked easily by varying ε in the same dark matter model. We find that a high ε WDM and a low ε CDM model – which provide equally good fits to the z = 4 UV luminosity function – exhibit nearly identical evolution in the cosmic stellar mass and star formation rate densities. We show that differences in the star formation rate at fixed stellar mass are larger for variations in ε in a given dark matter model than they are between dark matter models; however, the scatter in star formation rates is larger between the two models than they are when varying ε. Our results suggest that JWST will likely be more informative in constraining baryonic processes operating in high-z galaxies than it will be in constraining the nature of dark matter.

中文翻译：

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重子和暗物质之间的简并：用 JWST 约束暗物质性质的挑战

詹姆斯韦伯太空望远镜（JWST）将彻底改变我们对早期星系形成的理解，并可能对暗物质的性质设定严格的限制。我们使用星系形成的半经验模型来研究重子物理学实施中的不确定性可能在多大程度上退化，并预测两种不同的暗物质模型——冷暗物质 (CDM) 和 7 keV 无菌中微子，它表现为暖暗物质（WDM）。我们的模型使用两个单独的尘埃衰减处方校准到在 z = 4 处观察到的紫外光度函数，这表现为低质量晕中的高和低恒星形成效率。这些效率捕捉到了调节恒星形成过程的净效应。我们发现，在固定恒星形成效率 ε 下，在高 z 的两个暗物质模型中，微弱星系的丰度存在显着差异；这些差异很容易通过在同一个暗物质模型中改变 ε 来模拟。我们发现，高 ε WDM 和低 ε CDM 模型——它们对 z = 4 紫外光度函数提供了同样好的拟合——在宇宙恒星质量和恒星形成率密度方面表现出几乎相同的演变。我们表明，在给定的暗物质模型中，固定恒星质量下恒星形成率的差异比暗物质模型之间的差异更大；然而，两个模型之间恒星形成率的分散比改变 ε 时更大。