# AMI SZ observation of galaxy-cluster merger CIZA J2242+5301: perpendicular flows of gas and dark matter

## TL;DR

This study uses AMI SZ observations combined with lensing and X-ray data to explore the behavior of gas and dark matter during a galaxy cluster merger, revealing perpendicular gas flows and challenging modified gravity theories.

## Contribution

It provides new observational evidence of gas dynamics perpendicular to the merger axis, supporting the role of dark matter in galaxy cluster mergers.

## Key findings

- High pressure gas elongated perpendicular to the merger axis
- Gas pushed into linear structures during core passage
- Results challenge modified gravity theories without dark matter

## Abstract

AMI observations towards CIZA J2242+5301, in comparison with observations of weak gravitational lensing and X-ray emission from the literature, are used to investigate the behaviour of non-baryonic dark matter (NBDM) and gas during the merger. Analysis of the Sunyaev-Zel'dovich (SZ) signal indicates the presence of high pressure gas elongated perpendicularly to the X-ray and weak-lensing morphologies which, given the merger-axis constraints in the literature, implies that high pressure gas is pushed out into a linear structure during core passing. Simulations in the literature closely matching the inferred merger scenario show the formation of gas density and temperature structures perpendicular to the merger axis. These SZ observations are challenging for modified gravity theories in which NBDM is not the dominant contributor to galaxy-cluster gravity.