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

Institute of Theoretical Astrophysics, University of Oslo, Postboks 1029, 0315 Oslo, Norway
e-mail: maxbg@astro.uio.no

Received: 30 July 2013
Accepted: 15 November 2013

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 with the code Isis, which includes scalar fields, to analyse the deviation of observables in modified gravity models with respect to ΛCDM.

Results. We find that the presence of the screening makes the deviation 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 haloes with masses between 10¹³  M_⊙   h^-1 and 10¹⁴  M_⊙   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 haloes are screened, there could also be a weaker gravitational redshift.