Probing theories of gravity with phase space-inferred potentials of galaxy clusters

Abstract

Modified theories of gravity provide us with a unique opportunity to generate innovative tests of gravity. In Chameleon f (R) gravity, the gravitational potential differs from the weak-field limit of general relativity (GR) in a mass dependent way. We develop a probe of gravity which compares high mass clusters, where Chameleon effects are weak, to low mass clusters, where the effects can be strong. We utilize the escape velocity edges in the radius/velocity phase space to infer the gravitational potential profiles on scales of 0.3 -1 virial radii. We show that the escape edges of low mass clusters are enhanced compared to GR, where the magnitude of the difference depends on the background field value |fR0|. We validate our probe using N-body simulations and simulated light cone galaxy data. For a DESI (Dark Energy Spectroscopic Instrument) Bright Galaxy Sample, including observational systematics, projection effects, and cosmic variance, our test can differentiate between GR and Chameleon f (R) gravity models, |fR0| = 4 × 10 −6 (2 × 10 −6 ) at > 5σ (> 2σ), more than an order of magnitude better than current cluster-scale constraints.

On Escaping a Galaxy Cluster in an Accelerating Universe

“…In particular, as demonstrated in Miller et al (2016), this offset ends up overestimating the potential by ∼20%. Following Behroozi et al (2013), we define the equivalence radius to be the point at which the acceleration due to the gravitational potential of the cluster and the acceleration of the expanding universe are equivalent Setting the boundary condition such that the escape velocity must necessarily be zero at the equivalence radius, , and using Equation (1), we find This reproduces the result shown in Stark et al (2016) and Miller et al (2016). From now on we refer to this escape velocity profile as Einasto qH 2 .…”

A general framework to test gravity using galaxy clusters – I. Modelling the dynamical mass of haloes in f(R) gravity

“…A more recent analysis can be found in Pizzuti et al (2017). The dynamical mass or potential can also be inferred from the escape velocity edges in the radius/velocity phase space, which can be compared with the lensing-inferred mass profile, or the gravitational potential profiles for samples of low-and high-mass haloes, which would feel different effects of gravity due to the chameleon screening, can be compared (Stark et al 2016).…”

Marked clustering statistics in f(R) gravity cosmologies

“…From the observational point of view, we can measure the Newtonian gravitational potential from the X-ray temperature of galaxy clusters (see e.g., Allen et al 2004Allen et al , 2008Li et al 2016), the gas mass fractions of clusters and the escape velocity profile, v esc (r) (Stark et al 2016). Hence, if we reconstruct the gravitational potential from the observations mentioned above and use a mark that is a function of the potential, similar to Eqn.…”