Wide-angle effects in multi-tracer power spectra with Doppler corrections

TL;DR

This paper develops a comprehensive framework for calculating wide-angle corrections to multi-tracer galaxy power spectra, incorporating relativistic Doppler effects and providing new analytical methods for integrals involving spherical Bessel functions, crucial for large-scale surveys.

Contribution

It introduces the first detailed derivation of wide-angle cross-power spectra with Doppler magnification and presents a novel analytical approach for integrals of spherical Bessel functions with general window functions.

Findings

Inclusion of Doppler effects is essential for accurate wide-angle corrections.

Derived analytical expressions for wide-angle cross-power spectra involving Doppler magnification.

Developed a new method for integrating functions against pairs of spherical Bessel functions.

Abstract

We examine the computation of wide-angle corrections to the galaxy power spectrum including redshift-space distortions and relativistic Doppler corrections, and also including multiple tracers with differing clustering, magnification and evolution biases. We show that the inclusion of the relativistic Doppler contribution, as well as radial derivative terms, are crucial for a consistent wide-angle expansion for large-scale surveys, both in the single and multi-tracer cases. We also give for the first time the wide-angle cross-power spectrum associated with the Doppler magnification-galaxy cross correlation, which has been shown to be a new way to test general relativity. In the full-sky power spectrum, the wide-angle expansion allows integrals over products of spherical Bessel functions to be computed analytically as distributional functions, which are then relatively simple to integrate over. We give for the first time a complete discussion and new derivation of the finite part of the divergent integrals of the form $\int_{0}^{\infty} \mathrm{d} r r^{n} j_{\ell}(k r) j_{\ell^{\prime}}(q r)$, which are necessary to compute the wide-angle corrections when a general window function is included. This facilitates a novel method for integrating a general analytic function against a pair of spherical Bessel functions.