Nuclear Activity in Circumnuclear Ring Galaxies

TL;DR

This study investigates the link between circumnuclear rings and nuclear activity in galaxies, revealing that CNRs are more related to intrinsic galaxy properties and minor mergers, and are associated with increased Seyfert activity and specific AGN types.

Contribution

It provides new insights into the connection between circumnuclear rings and AGN activity, highlighting the role of intrinsic properties and minor mergers in CNR formation.

Findings

CNRs are more related to intrinsic properties or minor mergers than to bright companions.

Higher incidence of strong bars in AGN with CNRs than expected.

Increased rate of Seyfert activity in galaxies with CNRs, especially Sy 2 types.

Abstract

We have analyzed the frequency and properties of the nuclear activity in a sample of galaxies with circumnuclear rings and spirals (CNRs). This sample was compared with a control sample of galaxies with very similar global properties but without circumnuclear rings. We discuss the relevance of the results in regard to the AGN feeding processes and present the following results: (i) bright companion galaxies seem not to be important for the appearance of CNRs, which appear to be more related to intrinsic properties of the host galaxies or to minor merger processes; (ii) the proportion of strong bars in galaxies with an AGN and a CNR is somewhat higher than the expected ratio of strongly barred AGN galaxies from the results of Ho and co-workers; (iii) the incidence of Seyfert activity coeval with CNRs is clearly larger than the rate expected from the morphological distribution of the host galaxies; (iv) the rate of Sy 2 to Sy 1 type galaxies with CNRs is about three times larger than the expected ratio for galaxies without CNRs and is opposite to that predicted by the geometric paradigm of the classical unified model for AGNs, although it does support the hy-pothesis that Sy 2 activity is linked to circumnuclear star formation. The possible selection effects of the sample are discussed, and we conclude that the detected trends are strong enough to justify high quality observations of as large as possible sets of galaxies with circumnuclear rings and their matched control samples.