利用大尺度结构中的相对论效应约束星系种群的天体物理性质
Using relativistic effects in large-scale structure to constrain astrophysical properties of galaxy populations
AI总结：
研究提出利用星系两点相关函数中的相对论奇数多极与牛顿偶数多极，通过交叉相关划分的亮暗样本来约束演化与放大偏置，该方法可在中等尺度提供不受污染的纯净测量。
摘要：
即将开展的大尺度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畸变的细微修正，当交叉相关暗物质的两种不同示踪物时，会以偶极和八极的形式出现。偶极和八极对观测示踪物的演化偏置和放大偏置非常敏感，而这些偏置很难准确建模，因为它们取决于巡天通量极限处光度函数的导数。我们表明，将星系种群划分为亮样本和暗样本使我们能够对它们进行交叉相关，并利用相关函数的相对论奇数多极与偶数牛顿多极一起约束这两个样本的演化偏置和放大偏置。尽管八极的信噪比远低于偶极，但它通过打破参数简并性显著改善了约束。我们在使用平方公里阵列的未来巡天场景中说明了这一点，并展示了以不同方式划分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物以增进对其光度函数的了解。此外，偶极和八极的信噪比在中等尺度上达到峰值，这意味着它们可以提供对放大偏置和演化偏置的纯净测量，而不会受到局部原初非高斯性或非常大尺度上系统误差的污染。
英文摘要：
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 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.
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