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arXiv 0907.0282astro-ph.CO
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用双谱方法确定大尺度下的星系偏差因子

Determine the galaxy bias factors on large scales using bispectrum method

Hong Guo, Y. P. Jing

摘要:

本文研究了从星系的功率谱和双谱中是否可以无偏地恢复星系的偏置因子。我们使用一组数值N体模拟,并构建基于Croton等人(2006)的半解析模型的大型模拟星系目录。我们测量了不同光度星系的约化双谱,并从它们的双谱中确定了线性和第一非线性偏置因子。我们发现,在波数k=0.1h/Mpc的大尺度下,偏置因子b_1和b_2几乎为常数,用双谱方法得到的b_1与期望值吻合得很好。非线性偏置因子b2为负值,除了M<-23的最亮星系有正值b2。星系b2的行为与其宿主晕的b2质量依赖性是一致的。我们表明,它是必不可少的,以有一个准确的估计的暗物质双谱的b1和b2的无偏测量。我们还测试了结合晕占据分布来模拟星系功率谱和双谱的分析方法。根据当前宇宙学研究的精度要求,晕模型的预言与模拟结果并不吻合。

英文摘要:

We study whether the bias factors of galaxies can be unbiasedly recovered from their power spectra and bispectra. We use a set of numerical N-body simulations and construct large mock galaxy catalogs based upon the semi-analytical model of Croton et al. (2006). We measure the reduced bispectra for galaxies of different luminosity, and determine the linear and first nonlinear bias factors from their bispectra. We find that on large scales down to that of the wavenumber k=0.1h/Mpc, the bias factors b1 and b2 are nearly constant, and b1 obtained with the bispectrum method agrees very well with the expected value. The nonlinear bias factor b2 is negative, except for the most luminous galaxies with M<-23 which have a positive b2. The behavior of b2 of galaxies is consistent with the b2 mass dependence of their host halos. We show that it is essential to have an accurate estimation of the dark matter bispectrum in order to have an unbiased measurement of b1 and b2. We also test the analytical approach of incorporating halo occupation distribution to model the galaxy power spectrum and bispectrum. The halo model predictions do not fit the simulation results well on the precision requirement of current cosmological studies.

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