An Offset Seyfert 2 Nucleus in the Minor Merger System NGC 3341

TL;DR

This paper reports the discovery of an offset Seyfert 2 nucleus in the minor merger galaxy NGC 3341, indicating that black hole activity can be triggered in dwarf secondary galaxies during mergers.

Contribution

It provides the first evidence of an active nucleus in a dwarf galaxy within a minor merger, highlighting the role of such interactions in black hole activity.

Findings

Detection of a Seyfert 2 nucleus in the secondary galaxy

Identification of a LINER-like offset nucleus

Implication that minor mergers can trigger black hole accretion

Abstract

We present the discovery of a triplet of emission-line nuclei in the disturbed disk galaxy NGC 3341, based on archival data from the Sloan Digital Sky Survey and new observations from the Keck Observatory. This galaxy contains two offset nuclei within or projected against its disk, at projected distances of 5.1 and 8.4 kpc from its primary nucleus and at radial velocity separation of less than 200 km/s from the primary. These appear to be either dwarf ellipticals or the bulges of low-mass spirals whose disks have already been stripped off while merging into the primary galaxy. The inner offset nucleus has a Seyfert 2 spectrum and a stellar velocity dispersion of 70+/-7 km/s. The outer offset nucleus has very weak emission lines consistent with a LINER classification, and the primary nucleus has an emission-line spectrum close to the boundary between LINER/HII composite systems and HII nuclei; both may contain accreting massive black holes, but the optical classifications alone are ambiguous. The detection of an offset active nucleus in NGC 3341 provides a strong suggestion that black hole accretion episodes during minor mergers can be triggered in the nuclei of dwarf secondary galaxies as well as in the primary.