Gravitational Redshift Constraints on the Effective Theory of Interacting Dark Energy

TL;DR

Upcoming galaxy surveys can utilize gravitational redshift measurements to significantly improve constraints on interacting dark energy models, especially those breaking the weak equivalence principle, by analyzing galaxy clustering dipoles.

Contribution

This work demonstrates how gravitational redshift enhances parameter constraints in the effective theory of interacting dark energy, introducing a new method tested with a publicly available Python package.

Findings

Gravitational redshift dipole breaks degeneracies in dark energy parameters.

Constraints improve by up to 50% with gravitational redshift data.

The Python package EF-TIGRE is released for community use.

Abstract

Upcoming galaxy surveys provide the necessary sensitivity to measure gravitational redshift, a general relativistic effect that generates a dipole in galaxy clustering data when correlating two distinct populations of galaxies. Here, we study the constraining power of gravitational redshift within the framework of the effective theory of interacting dark energy. This formalism describes linear cosmological perturbations in scalar-tensor theories of gravity with a limited number of free functions, and allows each particle species to be coupled differently to the gravitational sector. In this work, we focus on Horndeski theories with a non-minimal coupling of dark matter to the scalar degree of freedom, yielding a breaking of the weak equivalence principle for this cosmic component, a scenario that is yet untested. We show that the dipole generated by gravitational redshift significantly breaks degeneracies and tightens the constraints on the parameters of the effective theory compared to the standard redshift-space distortion analysis solely based on the even multipoles in the galaxy correlation function, with an improvement of up to $\sim 50\%$ for populations with a galaxy bias difference equal to 1. We make the Python package EF-TIGRE (Effective Field Theory of Interacting dark energy with Gravitational REdshift) developed for this work publicly available.