TheXMMCluster Survey: testing chameleon gravity using the profiles of clusters

Abstract

The chameleon gravity model postulates the existence of a scalar field that couples with matter to mediate a fifth force. If it exists, this fifth force would influence the hot X-ray emitting gas filling the potential wells of galaxy clusters. However, it would not influence the clusters weak lensing signal. Therefore, by comparing X-ray and weak lensing profiles, one can place upper limits on the strength of a fifth force. This technique has been attempted before using a single, nearby cluster (Coma, z = 0.02, Terukina et al. 2014). Here we apply the technique to the stacked profiles of 58 clusters at higher redshifts (0.1 < z < 1.2 ), including 12 new to the literature, using X-ray data from the XMM Cluster Survey (XCS) and weak lensing data from the Canada France Hawaii Telescope Lensing Survey (CFHTLenS). Using a multiparameter MCMC analysis, we constrain the two chameleon gravity parameters (β and φ ∞ ). Our fits are consistent with general relativity, not requiring a fifth force. In the special case of f (R) gravity (where β = 1/6), we set an upper limit on the background field amplitude today of |f R0 |< 6 × 10 −5 (95% CL). This is one of the strongest constraints to date on |f R0 | on cosmological scales. We hope to improve this constraint in future by extending the study to hundreds of clusters using data from the Dark Energy Survey.

Breaking the Vainshtein screening in clusters of galaxies

“…(16) should be more properly named as thermal pressure-supported HSE mass; but non-thermal contributions might arise as, for example, among other, bulk motions, turbulences, cosmic rays, and magnetic fields. In GR, the non-thermal contribution are derived and parameterized from numerical simulations; thus, in order to be taken in consideration when an alternative gravity scenario is studied, one should, in principle, run the same simulations and find for a new parametrization [97,98,105]. The approach followed by [40] is slightly different: they use the Joint Analysis of Cluster Observations (JACO) code from [70], which may provide a simultaneous fit of many kinds of observations related to clusters of galaxies, like X-ray, Sunyaev-Zeldovich and weak-lensing data, once parametric models for matter components are considered.…”

Cosmological simulations with hydrodynamics of screened scalar-tensor gravity with non-universal coupling

“…The temperature is a very interesting component to study due to its close relation observables (Wilcox et al 2015;Terukina et al 2014). The temperature is not an output of our code and needs to be reconstructed using the ideal gas law,…”

“…With these modified gravity theories comes the challenge of finding methods to test them against observations (Terukina et al 2014;Wilcox et al 2015). Theorists in the past have mainly used predictions from models and simulations that only include dark matter due to the simplistic nature of dark matter, when constraining modified gravity theories.…”

Kinetic Sunyaev-Zel’dovich effect in modified gravity

“…In particular, viable fðRÞ models have been constrained with secondary CMB anisotropies, such as CMB lensing, the integrated Sachs-Wolfe effect [7,8] and its cross-correlation with galaxy density [9,10], galaxy cluster abundances [11][12][13] and profiles [14,15], galaxy power spectrum [16,17], redshift-space distortions from spectroscopic surveys [18][19][20], weak gravitational lensing [21,22], 21-cm intensity mapping [23], and dwarf galaxies [24,25].…”