标题： 星系的非线性红移空间功率谱 显示英文标题

标题： The nonlinear redshift-space power spectrum of galaxies

摘要： 我们研究红移空间中星系的功率谱，使用三阶微扰理论来包含线性理论中缺失的修正项。 我们假设星系存在局部偏差：即星系密度是从底层质量分布的某个局部函数中采样的。 我们发现真实空间中非线性偏差的影响是引入两个新特征：首先，功率中存在一个与波数无关的贡献，我们揭示其本质基本上是一个散粒噪声项。 原则上，这一贡献可能会掩盖原始功率谱，并可能限制后者在非常大尺度上测量的准确性。 其次，二阶和三阶偏差的影响是修改有效偏差（定义为星系功率谱与物质功率谱比值的平方根）。 有效偏差在广泛的尺度范围内几乎是尺度无关的。 这些一般结论也适用于红移空间。 此外，我们研究了特殊速度对功率谱的扭曲，这可能用于约束宇宙的密度。 我们考察了四极矩与单极矩的比率，并发现高阶项可以模仿线性理论偏差，但所暗示的偏差既不是线性偏差，也不是上述的有效偏差。 我们通过有偏差的N体模拟测试了该理论，在真实空间和红移空间中都得到了很好的一致性，前提是局部偏差是在其分数均方根密度涨度为$< 0.5$的尺度上应用的。 显示英文摘要

摘要： We study the power spectrum of galaxies in redshift space, with third order perturbation theory to include corrections that are absent in linear theory. We assume a local bias for the galaxies: i.e. the galaxy density is sampled from some local function of the underlying mass distribution. We find that the effect of the nonlinear bias in real space is to introduce two new features: first, there is a contribution to the power which is constant with wavenumber, whose nature we reveal as essentially a shot-noise term. In principle this contribution can mask the primordial power spectrum, and could limit the accuracy with which the latter might be measured on very large scales. Secondly, the effect of second- and third-order bias is to modify the effective bias (defined as the square root of the ratio of galaxy power spectrum to matter power spectrum). The effective bias is almost scale-independent over a wide range of scales. These general conclusions also hold in redshift space. In addition, we have investigated the distortion of the power spectrum by peculiar velocities, which may be used to constrain the density of the Universe. We look at the quadrupole-to-monopole ratio, and find that higher-order terms can mimic linear theory bias, but the bias implied is neither the linear bias, nor the effective bias referred to above. We test the theory with biased N-body simulations, and find excellent agreement in both real and redshift space, providing the local biasing is applied on a scale whose fractional r.m.s. density fluctuations are $< 0.5$.