# Observational evidence for bar formation in disk galaxies via cluster-cluster interaction

## TL;DR

This study provides observational evidence that galaxy cluster interactions can trigger bar formation in disk galaxies, highlighting a large-scale external mechanism alongside internal processes.

## Contribution

It demonstrates that cluster-cluster interactions significantly increase the fraction of barred disk galaxies, suggesting a new external mechanism for bar formation.

## Key findings

- Barred galaxy fraction is 1.5 times higher in interacting clusters.
- 42% of galaxies in interacting clusters are barred.
- Cluster interactions are an important mechanism for bar formation.

## Abstract

Bars are an elongated structure that extends from the centre of galaxies, and about one-third of disk galaxies are known to possess bars. These bars are thought to form either through a physical process inherent in galaxies, or through an external process such as galaxy-galaxy interactions. However, there are other plausible mechanisms of bar formation that still need to be observationally tested. Here we present the observational evidence that bars can form via cluster-cluster interaction. We examined 105 galaxy clusters at redshift $0.015 < z < 0.060$ that are selected from the Sloan Digital Sky Survey data, and identified 16 interacting clusters. We find that the barred disk-dominated galaxy fraction is about 1.5 times higher in interacting clusters than in clusters with no clear signs of ongoing interaction (42% versus 27%). Our result indicates that bars can form through a large-scale violent phenomenon, and cluster-cluster interaction should be considered an important mechanism of bar formation.