Abstract
ABSTRACT We test two methods, including one that is newly proposed in this work, for correcting for the effects of chameleon f(R) gravity on the scaling relations between the galaxy cluster mass and four observable proxies. Using the first suite of cosmological simulations that simultaneously incorporate both full physics of galaxy formation and Hu-Sawicki f(R) gravity, we find that these rescaling methods work with a very high accuracy for the gas temperature, the Compton Y-parameter of the Sunyaev–Zel’dovich (SZ) effect and the X-ray analogue of the Y-parameter. This allows the scaling relations in f(R) gravity to be mapped to their Λ cold dark matter counterparts to within a few per cent. We confirm that a simple analytical tanh formula for the ratio between the dynamical and true masses of haloes in chameleon f(R) gravity, proposed and calibrated using dark-matter-only simulations in a previous work, works equally well for haloes identified in simulations with two very different – full-physics and non-radiative – baryonic models. The mappings of scaling relations can be computed using this tanh formula, which depends on the halo mass, redshift, and size of the background scalar field, also at a very good accuracy. Our results can be used for accurate determination of the cluster mass using SZ and X-ray observables, and will form part of a general framework for unbiased and self-consistent tests of gravity using data from present and upcoming galaxy cluster surveys. We also propose an alternative test of gravity, using the YX–temperature relation, which does not involve mass calibration.
Highlights
Clusters of galaxies are the largest gravitationally bound objects in the Universe and, as tracers of the highest peaks of the primordial density perturbations, they are frequently used to test cosmological models
There we will present an example in which we map between the general relativity (GR) and f(R) mass scaling relations based on this approximate fitting formula, rather than the actual values of Mdfy(nR)/Mtfru(eR) from the simulations
Accurate determination of the cluster mass is a vital requirement of tests that use large-scale structures (LSS) probes including cluster counts to constrain cosmological models
Summary
Clusters of galaxies are the largest gravitationally bound objects in the Universe and, as tracers of the highest peaks of the primordial density perturbations, they are frequently used to test cosmological models. These are modified by the effects of the fifth force on the gravitational potentials of haloes, which are intrinsically linked to the dynamical mass and gas temperature According to He & Li (2016), who employed a suite of non-radiative simulations to investigate the effect of f(R) gravity on a number of mass proxies, it is possible to map between the scaling relations in f(R) gravity and GR using only the relation between the dynamical and true (or lensing) masses of a halo, which is accurately captured by our tanh fitting formula mentioned above (cf Fig. 1). The paper is organized as follows: in Section 2, several important aspects of the f(R) gravity theory are introduced, and we summarize the scaling relation mappings proposed by He & Li (2016) and our novel alternative mappings; in Section 3, we describe our simulations and calculations of the halo masses and observable proxies; in Section 4, we present our results for the scaling relations of four mass proxies; in Section 5, we summarize the results of this work and their significance for our framework
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