Measuring the Nonlinear Biasing Function from a Galaxy Redshift Survey
Measuring the Nonlinear Biasing Function from a Galaxy Redshift Survey
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从星系红移巡天测量非线性偏置函数
DOI：
10.1086/309331
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发表时间：
2000
期刊：
影响因子：
--
通讯作者：
A. Dekel
中科院分区：
文献类型：
--
作者：
Y. Sigad;E. Branchini;A. Dekel
本文提出了一种简单的方法，从红移巡天中估算星系的非线性偏置函数。这种非线性偏置的特征是在给定质量密度涨落δg的情况下，星系密度涨落的条件平均值|或通过相关的平均偏置和非线性参数。利用宇宙学模拟中的星系分布，在几个Mpc的平滑下，我们发现，|尽管存在偏置散射，但δ g可以从星系和质量的累积分布函数Cg（δg）和C（δ）中恢复到很好的精度。然后，使用一套不同宇宙学模型的模拟，我们证明了C（δ）可以在轻度非线性区域中近似为具有单个参数σ的1 + δ的累积对数正态分布，与Cg和C之间的差异相比，偏差很小。最后，我们展示了如何直接从红移空间中观测到的Cg中以足够的精度获得非线性偏置函数。因此，一旦假定适当尺度的均方根质量波动是先验的，就可以从细胞中的计数获得偏置函数。不同星系类型之间的相对偏置函数也可以用类似的方法测量。误差的主要来源是稀疏采样，这要求平均星系间隔小于平滑尺度。一旦应用于红移巡天，如点源目录红移巡天（PSCz），二度场（2dF），斯隆数字巡天（SDSS），或深河外星系演化探测器（DEEP），偏置函数可以提供有价值的约束星系的形成和结构演化。
We present a simple method for evaluating the nonlinear biasing function of galaxies from a redshift survey. The nonlinear biasing is characterized by the conditional mean of the galaxy density fluctuation given the underlying mass density fluctuation ⟨δg|δ⟩, or by the associated parameters of mean biasing, , and nonlinearity, . Using the distribution of galaxies in cosmological simulations, at a smoothing of a few Mpc, we find that ⟨δg|δ⟩ can be recovered to a good accuracy from the cumulative distribution functions of galaxies and mass, Cg(δg) and C(δ), despite the biasing scatter. Then, using a suite of simulations of different cosmological models, we demonstrate that C(δ) can be approximated in the mildly nonlinear regime by a cumulative lognormal distribution of 1 + δ with a single parameter σ, with deviations that are small compared to the difference between Cg and C. Finally, we show how the nonlinear biasing function can be obtained with adequate accuracy directly from the observed Cg in redshift space. Thus, the biasing function can be obtained from counts in cells once the rms mass fluctuation at the appropriate scale is assumed a priori. The relative biasing function between different galaxy types is measurable in a similar way. The main source of error is sparse sampling, which requires that the mean galaxy separation be smaller than the smoothing scale. Once applied to redshift surveys such as the Point Source Catalog Redshift Survey (PSCz), the Two-Degree Field (2dF), Sloan Digital Sky Survey (SDSS), or the Deep Extragalactic Evolutionary Probe (DEEP), the biasing function can provide valuable constraints on galaxy formation and structure evolution.