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

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 cosmological simulations, we find that in modified gravity the mass-temperature relation varies significantly from the standard gravity prediction 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 at massive, hot galaxy clusters. We further investigate the mass-temperature relation for other mass estimates than the thermal mass estimate, and discover that the gas mass-temperature results show an even more significant deviations from Einstein's gravity than the thermal mass-temperature.Article number, page 1 of 9

Mass-temperature relation in ΛCDM and modified gravity

“…(35)] and the model by Ref. [90] with that of [74] for f (R) and symmetron models. For f (R) models, we consider n = 1 and |f R0 | = 10 −4 , 10 −5 , 10 −6 , while for the symmetron model (β, a SSB , λ 0 ) = (1.0, 0.5, 1.0) for Sym A, (1.0, 0.33, 1.0) for Sym B, (2.0, 0.5, 1.0) for Sym C, and (1.0, 0.25, 1.0) for Sym D.…”

“…In all the panels, the black straight dashed line represents the classical MTR self-similar behavior and the black solid line the ΛCDM model obtained in the simulations of Ref. [74] and for the specific modified gravity models we refer to the caption of Fig. 1.…”

“…In order to get the MTR for f (R) and symmetron models, Ref. [74] modified the ISIS code [80] and ran two sets of simulations, one for f (R)-gravity models and another one for the symmetron models, both containing 256 3 DM particles. The box size and background cosmology were different for the two models, due to consistency with previous works of the authors [87].…”

“…By means of hydrodynamic simulations, Ref. [74] showed that the MTR obtained in MG theories is different from the expectations of GR. 2 In the present paper, we extended the results of Ref.…”

“…Effects of MG can be probed with structure formation and verified by means of dark-matter-only N -body simulations [77][78][79][80][81]. Nevertheless, hydrodynamical simulations are more suited from an observational point of view, as they provide observables, such as the halo profile, the turnaround [82,83], the splashback radius [84], and the mass-temperature relation (MTR) [74] which can be directly compared with observations. While the halo profile is usually studied in DM-only simulations and it is, as such, used for a variety of studies, the MTR can be accurately inferred only with hydrodynamic simulations, to avoid the necessary approximations introduced, for example, by using scaling relations.…”