A general relativistic signature in the galaxy bispectrum: the local effects of observing on the lightcone
A general relativistic signature in the galaxy bispectrum: the local effects of observing on the lightcone
复制标题
星系双谱中的一般相对论特征：光锥观测的局部效应
DOI：
10.1088/1475-7516/2017/03/034
复制
发表时间：
2016
影响因子：
6.4
通讯作者：
C. Clarkson
中科院分区：
文献类型：
--
作者：
Obinna Umeh;Sheean Jolicoeur;R. Maartens;C. Clarkson
下一代星系调查将越来越多地依靠星系双谱来改善宇宙学限制，特别是原始的非高斯性。一个有待发展的关键理论要求是分析一般相对论对双谱的影响，双谱是由于在过去的光锥上观察星系而产生的，以及来自对动力学的相对论修正。作为对星系双谱进行完全相对论分析的第一步，我们首次计算了来自多普勒势和引力势贡献的局域相对论光锥对双谱的影响。对于星系双谱，这个问题比功率谱复杂得多，因为我们需要二阶光锥修正。二阶模式耦合的贡献意味着相对论修正在比功率谱更小的尺度上是不可忽略的。在原始高斯宇宙中，z∼1处压缩形状的局域光锥投影效应意味着当短模为k≳(50Mpc)≲1时，双谱与牛顿预言相差10%。如果在观测分析中忽略这些相对论投影效应，则可能被误认为原始的非高斯性。为了准确测量原始的非高斯性，对于即将到来的探测相等尺度和超越尺度的调查，所有的相对论光锥效应和相对论动力学修正都应该包括在内。
Next-generation galaxy surveys will increasingly rely on the galaxy bispectrum to improve cosmological constraints, especially on primordial non-Gaussianity. A key theoretical requirement that remains to be developed is the analysis of general relativistic effects on the bispectrum, which arise from observing galaxies on the past lightcone, as well as from relativistic corrections to the dynamics. As an initial step towards a fully relativistic analysis of the galaxy bispectrum, we compute for the first time the local relativistic lightcone effects on the bispectrum, which come from Doppler and gravitational potential contributions. For the galaxy bispectrum, the problem is much more complex than for the power spectrum, since we need the lightcone corrections at second order. Mode-coupling contributions at second order mean that relativistic corrections can be non-negligible at smaller scales than in the case of the power spectrum. In a primordial Gaussian universe, we show that the local lightcone projection effects for squeezed shapes at z ∼ 1 mean that the bispectrum can differ from the Newtonian prediction by ≳ 10% when the short modes are k ≲ (50 Mpc)−1. These relativistic projection effects, if ignored in the analysis of observations, could be mistaken for primordial non-Gaussianity. For upcoming surveys which probe equality scales and beyond, all relativistic lightcone effects and relativistic dynamical corrections should be included for an accurate measurement of primordial non-Gaussianity.