Probing modified gravity via the mass-temperature relation of galaxy clusters

Institute of Theoretical Astrophysics, University of Oslo, PO Box 1029, Blindern, 0315 Oslo, Norway
e-mail: amirham@astro.uio.no; d.f.mota@astro.uio.no

Received: 26 May 2016
Accepted: 11 October 2016

Abstract

We propose that the mass-temperature relation of galaxy clusters is a prime candidate for testing gravity theories beyond Einstein’s general relativity, for modified gravity models with universal coupling between matter and the scalar field. For non-universally coupled models, we discover that the impact of modified gravity can remain hidden from the mass-temperature relation. Using non-radiative hydrodynamic cosmological simulations, we find that in modified gravity the hydrostatic mass-temperature relation varies significantly from the standard gravity relation of M ∝ T^1.73. To be specific, for symmetron models with a coupling factor of β = 1 we find a lower limit to the power law as M ∝ T^1.6; and for f(R) gravity we compute predictions based on the model parameters. We show that the mass-temperature relation, for screened modified gravities, is significantly different from that of standard gravity for the less massive and colder galaxy clusters, while being indistinguishable from Einstein’s gravity for massive, hot galaxy clusters. We further investigate the mass-temperature relation for other mass estimates than the hydrostatic mass estimate and discover that the gas mass-temperature results show even more significant deviations from Einstein’s gravity than the hydrostatic mass-temperature.