# Testing Emergent Gravity with Optical, X-ray, and Weak Lensing Measurements in Massive, Relaxed Galaxy Clusters

## TL;DR

This study tests Emergent Gravity predictions against observations of relaxed galaxy clusters using optical, X-ray, and lensing data, finding discrepancies at larger radii and questioning its viability compared to dark matter models.

## Contribution

It incorporates the brightest cluster galaxy into the analysis, providing a more comprehensive test of Emergent Gravity against observational data.

## Key findings

- Better agreement with observations in inner regions after including BCG
- Discrepancies of up to 6 times at larger radii
- Emergent Gravity less consistent with data than cold dark matter models

## Abstract

We test the predictions of Emergent Gravity using matter densities of relaxed, massive clusters of galaxies using observations from optical and X-ray wavebands. We improve upon previous work in this area by including the baryon mass contribution of the brightest cluster galaxy in each system, in addition to total mass profiles from gravitational lensing and mass profiles of the X-ray emitting gas from Chandra. We use this data in the context of Emergent Gravity to predict the "apparent" dark matter distribution from the observed baryon distribution, and vice-versa. We find that although the inclusion of the brightest cluster galaxy in the analysis improves the agreement with observations in the inner regions of the clusters ($r \lesssim 10-30$ kpc), at larger radii ($r \sim 100-200$ kpc) the Emergent Gravity predictions for mass profiles and baryon mass fractions are discrepant with observations by a factor of up to $\sim2-6$, though the agreement improves at radii near $r_{500}$. At least in its current form, Emergent Gravity does not appear to reproduce the observed characteristics of relaxed galaxy clusters as well as cold dark matter models.