AGNs in Small Galaxy Systems: comparing the main properties of active objects in pairs, triplets and groups

TL;DR

This study compares the properties and fractions of AGNs in small galaxy systems like pairs, triplets, and groups, revealing environment and interaction effects on AGN activity.

Contribution

It provides a comprehensive comparison of optical and mid-IR AGN fractions across different small galaxy system configurations, highlighting environmental influences.

Findings

Higher AGN fraction in pairs and triplets than in groups.

Powerful AGNs are twice as common as regular AGNs in pairs and triplets.

WISE AGNs in groups are less massive, younger, and have close companions.

Abstract

We perform a comparative study of AGNs in pairs, triplets and groups. To this end we use the Duplancic et al. catalogue of small galaxy systems and consider BPT and WHAN diagnostic diagrams to select optical AGNs. Also we identify mid-IR AGNs by using WISE data. We performed a comparison between the different AGN classification methodologies and study the AGN fraction in pairs, triplets, and groups with four to six members. We also analyse the main properties of Optical and mid-IR AGN hosts and the influence of environment on the active nuclei phenomena in these small galaxy systems. Our results show that, regardless the specifically adopted classification scheme, the fraction of AGN in pairs and triplets is always higher than the corresponding fraction in groups. Moreover, the fraction of powerful AGNs in pair and triplets is about twice the fraction of regular AGNs. We also find a remarkable difference between Optical and mid-IR AGNs in groups, where host galaxies of WISE AGNs are less massive and concentrated, with young stellar populations and blue colours. Also all WISE AGNs in groups have a very close companions and reside in an intermediate global density environment. Galaxy triplets show a larger AGN fraction for galaxies with a close nearest neighbours, while pairs present a nearly constant AGN fraction regardless the distance to the nearest companion. Our studies highlight the important role of interactions, besides the global environment dependence, in the activation of the AGN phenomenon in small galaxy systems.