第一个十亿年宇宙变化的灵活分析模型
A Flexible Analytic Model of Cosmic Variance in the First Billion Years
摘要：
宇宙方差是由于大尺度暗物质密度场的涨落而引起的星系数密度的内在散射。在这项工作中，我们提出了一个简单的分析模型的宇宙方差在高红移宇宙（$z\sim5-15$）。我们假设，星系的生长根据晕质量函数的演变，我们允许随大尺度环境而变化。我们的模型产生了一个合理的匹配，在这个时代观察到的紫外光度函数调节恒星形成通过恒星反馈，并假设紫外光度函数是由最近的恒星形成。我们发现，宇宙中的UVLF的方差是主导的差异在底层的暗物质晕人口，而不是晕吸积的差异或我们的恒星反馈模型的细节。我们还发现宇宙方差在未来的高$z$调查中占主导地位，除了最亮的源或在非常高的红移（$z \gtrsim 12$）。我们通过公共Python包galcv提供了各种红移、星等和测量区域的宇宙方差的线性近似。最后，我们介绍了一种新的方法，将先验宇宙方差的星系光度函数的估计，并证明它显着提高了重要的可观察到的约束。
英文摘要：
Cosmic variance is the intrinsic scatter in the number density of galaxies due to fluctuations in the large-scale dark matter density field. In this work, we present a simple analytic model of cosmic variance in the high redshift Universe ($z\sim5-15$). We assume that galaxies grow according to the evolution of the halo mass function, which we allow to vary with large-scale environment. Our model produces a reasonable match to the observed ultraviolet luminosity functions in this era by regulating star formation through stellar feedback and assuming that the UV luminosity function is dominated by recent star formation. We find that cosmic variance in the UVLF is dominated by the variance in the underlying dark matter halo population, and not by differences in halo accretion or the specifics of our stellar feedback model. We also find that cosmic variance dominates over Poisson noise for future high-$z$ surveys except for the brightest sources or at very high redshifts ($z \gtrsim 12$). We provide a linear approximation of cosmic variance for a variety of redshifts, magnitudes, and survey areas through the public Python package galcv. Finally, we introduce a new method for incorporating priors on cosmic variance into estimates of the galaxy luminosity function and demonstrate that it significantly improves constraints on that important observable.
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