Tidally induced bar-like galaxies in simulated clusters

Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, Bartycka 18, 00-716 Warsaw, Poland

^⋆ Corresponding author: lokas@camk.edu.pl

Received: 13 May 2025
Accepted: 15 August 2025

Abstract

One of the scenarios for bar formation in galaxies involves their interaction with a more massive companion. The stellar component is then transformed from a disk into a bar-like prolate spheroid. I investigated a subsample of 77 bar-like galaxies tidally induced in the cluster environment, selected among the previously studied sample of bar-like galaxies from the IllustrisTNG simulations. I present six clear, convincing examples of bar-like galaxies formed after an interaction with a progenitor of a massive brightest cluster galaxy (BCG) and describe the properties of their bars. For the whole sample, the time of bar formation is strongly correlated with and typically slightly greater than the time of the pericenter passage. All galaxies are strongly stripped of dark matter and gas, and their rotation is similarly diminished. A larger pericenter distance typically requires a higher host mass in order to transform the galaxy, but the interactions show no preference for prograde configurations. The final strength of the bars does not correlate with the amount of tidal stripping experienced because of the variety of initial properties of the progenitors and the subsequent evolution over the next pericenter passages. In spite of difficulties in the interpretation of some cases involving mergers and multiple interactions, the results confirm in the cosmological context the reality of tidal bar formation in cluster environments previously studied using controlled simulations.