Gravitational redshift profiles in the $f(R)$ and symmetron models

TL;DR

This study uses simulations to analyze how modified gravity models like $f(R)$ and symmetron affect gravitational redshift profiles in galaxy clusters, revealing mass-dependent deviations from general relativity due to screening effects.

Contribution

It provides the first detailed analysis of gravitational redshift profiles in $f(R)$ and symmetron models, highlighting the impact of screening mechanisms on observable signals.

Findings

Deviations in gravitational redshift depend strongly on halo mass.

Enhanced gravitational signals up to 50% in certain mass ranges.

Screening effects can lead to weaker redshift signals in some cases.

Abstract

Aims. We investigate the gravitational redshift in clusters of galaxies in the symmetron and Hu-Sawicky $f(R)$ models. The characteristic feature of both models is the screening mechanism that hides the fifth force in dense environments recovering general relativity. Methods. We use $N$-body simulations that were run using the code \texttt{Isis}, which includes scalar fields, to analyse the deviation of observables in modified gravity models with respect to $\Lambda$CDM. Results. We find that due to the presence of the screening, the deviation is highly dependent on the halo mass. For instance, the $f(R)$ parameters $|f_{R0}|=10^{-5}$, $n=1$ cause an enhancement of the gravitational signal by up to 50% for halos with masses between $10^{13}\,M_\odot h^{-1}$ and $10^{14}\,M_\odot h^{-1}$. The characteristic mass range where the fifth force is most active varies with the model parameters. The usual assumption is that the presence of a fifth force leads to a deeper potential well and thus, a stronger gravitational redshift. However, we find that in cases in which only the central regions of the halos are screened, there could also be a weaker gravitational redshift.