Hydrostatic equilibrium of X-ray gas in X-COP clusters with HMG

TL;DR

This study evaluates Hyperconical Modified Gravity (HMG) as an alternative to dark matter in explaining the hydrostatic equilibrium of hot gas in galaxy clusters, showing promising results beyond 500 kpc.

Contribution

It provides the first analysis of HMG's effectiveness in modeling hydrostatic equilibrium in galaxy clusters using high-resolution X-ray data.

Findings

HMG fits cluster gas data well beyond 500 kpc without parameter fitting.

HMG potentially explains cluster dynamics without dark matter.

Further research needed for smaller spatial scales.

Abstract

Modified Newtonian Dynamics (MOND) was originally proposed to model galaxy rotation curves without dark matter. However, MOND presents difficulties in explaining the Radial Acceleration Relation (RAR) observed in galaxy clusters, and moreover, it does not completely eliminate the need for dark matter, since it requires using non-luminous particles (e.g. cold molecular gas or durst, or neutrinos) to explain the observed hydrostatic equilibrium of the hot gas. Hyperconical Modified Gravity (HMG) offers a relativistic framework that recovers the success of MOND in galaxy rotation curves as a natural particular case, and it could potentially reconcile the above discrepancies without invoking any type of dark matter. This Letter analyses the performance of the HMG model for hydrostatic equilibrium in 12 X-COP galaxy clusters, with a special focus on five objects with available complete stellar mass information: A1795, A2029, A2142, A2319 and A644. Specifically, we used high-resolution X-ray data with which gas density and mass profiles were previously derived to constrain modified gravity models. Our results show that the hydrostatic equilibrium of analysed cluster gas is more naturally adjusted to the HMG model beyond 500 kpc without the need to fit parameters, but further research is required to expand to more spatial scales.