Upcoming large-scale structure surveys will be able to measure new features in the galaxy two point correlation function. Relativistic effects appear on large scales as subtle corrections to redshift-space distortions, showing up as a dipole and octupole when cross-correlating two different tracers of dark matter. The dipole and octupole are very sensitive to the evolution and magnification biases of the observed tracers which are hard to model accurately as they depend upon the derivative of the luminosity function at the flux limit of the survey. We show that splitting a galaxy population into bright and faint samples allows us to cross-correlate these and constrain both the evolution bias and magnification bias of the two samples — using the relativistic odd multipoles of the correlation function, together with the even Newtonian multipoles. Although the octupole has much lower signal-to-noise than the dipole, it significantly improves the constraints by breaking parameter degeneracies. We illustrate this in the case of a futuristic survey with the Square Kilometre Array, and demonstrate how splitting the samples in different ways can help improve constraints. This method is quite general and can be used on different types of tracers to improve knowledge of their luminosity functions. Furthermore, the signal-to-noise of the dipole and octupole peaks on intermediate scales, which means that they can deliver a clean measurement of the magnification bias and evolution bias without contamination from local primordial non-Gaussianities or from systematics on very large scales.

中文翻译：

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在大尺度结构中使用相对论效应来限制星系群的天体物理特性


即将到来的大规模结构巡天将能够测量星系两点相关函数中的新特征。相对论效应在大尺度上表现为对红移空间扭曲的微妙校正，在将暗物质的两个不同示踪剂交叉相关时表现为偶极子和八极子。偶极子和八极子对观察到的示踪剂的演变和放大偏差非常敏感，这些示踪剂很难准确建模，因为它们依赖于光度函数在测量的通量极限处的导数。我们表明，将星系群分成明亮和暗淡的样本可以让我们将这些样本交叉相关并限制两个样本的演化偏差和放大偏差——使用相关函数的相对论奇多极点，以及偶数牛顿多极点。尽管八极子的信噪比比偶极子低得多，但它通过打破参数简并来显著改善约束。我们以 Square Kilometre Array 的未来主义调查为例来说明这一点，并演示了以不同的方式分割样本如何帮助改善约束。这种方法非常通用，可用于不同类型的示踪剂，以提高对其光度函数的了解。此外，偶极子和八极子的信噪比峰值在中间尺度上，这意味着它们可以提供放大倍率偏差和演化偏差的清晰测量，而不会受到局部原始非高斯性或非常大尺度的系统学的污染。