Large-scale tidal effect on redshift-space power spectrum in a finite-volume survey

TL;DR

This paper investigates how large-scale tidal forces induce anisotropic distortions in galaxy distributions, affecting redshift-space power spectrum measurements and potentially confounding cosmological inferences in finite-volume surveys.

Contribution

It introduces a formalism to quantify the impact of large-scale tidal effects on the redshift-space power spectrum, highlighting their significance for galaxy survey analyses.

Findings

Large-scale tidal forces cause homogeneous anisotropic distortions.

These distortions mimic redshift-space distortions and Alcock-Paczynski effects.

Impact on power spectrum is significant for current and future surveys.

Abstract

Long-wavelength matter inhomogeneities contain cleaner information on the nature of primordial perturbations as well as the physics of the early universe. The large-scale coherent overdensity and tidal force, not directly observable for a finite-volume galaxy survey, are both related to the Hessian of large-scale gravitational potential and therefore of equal importance. We show that the coherent tidal force causes a homogeneous anisotropic distortion of the observed distribution of galaxies in all three directions, perpendicular and parallel to the line-of-sight direction. This effect mimics the redshift-space distortion signal of galaxy peculiar velocities, as well as a distortion by the Alcock-Paczynski effect. We quantify its impact on the redshift-space power spectrum to the leading order, and discuss its importance for the ongoing and upcoming galaxy surveys.