The Star Cluster Population of the Collisional Ring Galaxy NGC 922

TL;DR

This study analyzes the star cluster population in the collisional ring galaxy NGC 922 using HST imaging, models, and simulations, revealing young clusters, their distribution, and potential progenitors for faint fuzzy clusters.

Contribution

It provides a detailed characterization of star clusters in NGC 922, including age, mass, distribution, and formation history, with insights into galaxy interaction effects.

Findings

69% of clusters are younger than 7 Myr

Cluster luminosity function slope is 2.1-2.3

Presence of clusters as progenitors for faint fuzzy clusters

Abstract

We present a detailed study of the star cluster population detected in the galaxy NGC922, one of the closest collisional ring galaxies known to date, using HST/WFPC2 UBVI photometry, population synthesis models, and N-body/SPH simulations.We find that 69% of the clusters are younger than 7Myr, and that most of them are located in the ring or along the bar, consistent with the strong Halpha emission. The cluster luminosity function slope of 2.1-2.3 for NGC922 is in agreement with those of young clusters in nearby galaxies. Models of the cluster age distribution match the observations best when cluster disruption is considered. We also find clusters with ages (>50Myr) and masses (>10^5 Msun) that are excellent progenitors for faint fuzzy clusters. The images also show a tidal plume pointing toward the companion. Its stellar age from our analysis is consistent with pre-existing stars that were stripped off during the passage of the companion. Finally, a comparison of the star-forming complexes observed in NGC922 with those of a distant ring galaxy from the GOODS field indicates very similar masses and sizes, suggesting similar origins.