A study of interacting galaxies from the Arp-Madore Catalogue: Triggering of star formation and nuclear activity

TL;DR

This study uses spectroscopic data to analyze how galaxy interactions influence star formation and nuclear activity, showing that interactions significantly increase young stellar populations and AGN activity compared to isolated galaxies.

Contribution

It provides new observational evidence linking galaxy interactions with enhanced star formation and nuclear activity, using a well-defined sample and control group.

Findings

Interacting galaxies have a median of 55% young stellar populations.

Over half of interacting galaxies host active galactic nuclei.

Interactions significantly increase star formation and AGN activity.

Abstract

We present Gemini Multi-Object Spectrograph (GMOS) spectroscopic observations of 95 galaxies from the Arp & Madore (1987) catalogue of peculiar galaxies. These galaxies have been selected because they appear to be in pairs and small groups. These observations have allowed us to confirm that 60 galaxies are indeed interacting systems. For the confirmed interacting sample, we have built a matched control sample of isolated galaxies. We present an analysis of the stellar populations and nuclear activity in the interacting galaxies and compare them with the isolated galaxies. We find a median light (mass) fraction of 55% (10%) in the interacting galaxies coming from stellar populations younger than 2 Gyr and 28% (3%) in the case of the isolated galaxies. More than half of the interacting galaxies are dominated by this young stellar population, while the isolated ones have most of their light coming from older stellar populations. We used a combination of diagnostic diagrams (BPTs and WHAN) to classify the main ionization mechanisms of the gas. The interacting galaxies in our sample consistently show a higher fraction of active galactic nuclei (AGN) relative to the control sample, which ranges between 1.6 and 4 depending on the combination of diagnostic diagrams employed to classify the galaxies and the number of galaxies considered. Our study provides further observational evidence that interactions drive star formation and nuclear activity in galaxies and can have a significant impact on galaxy evolution.