Two Candidates for Dual AGN in Dwarf-Dwarf Galaxy Mergers

TL;DR

This study reports the discovery of two candidate dual AGN in dwarf-dwarf galaxy mergers, providing rare observational evidence for black hole activity during early galaxy interactions.

Contribution

First large-scale search identifying dual AGN candidates in dwarf galaxy mergers, highlighting their characteristics and potential for understanding early galaxy and black hole growth.

Findings

Both candidates show tidal features indicative of mergers.

Each has dual luminous X-ray sources likely from accreting black holes.

Infrared colors are consistent with active galactic nuclei.

Abstract

Dual AGN are important for understanding galaxy-merger-triggered fueling of black holes and hierarchical growth of structures. The least explored type of dual AGN are those associated with mergers of two dwarf galaxies. According to observations and cosmological simulations, dwarf galaxies are the most abundant type of galaxies in the early Universe and the galaxy merger rate is dominated by dwarfs. However, these mergers are generally too distant to be directly observed, and low-redshift dwarf-dwarf merger-related dual AGN are notoriously hard to find. In this paper, we present the first results of our large-scale search for this elusive type of object and the first two candidates for dual AGN in dwarf-dwarf mergers. Both objects exhibit tidal features (tails and bridges) characteristic of galaxy mergers/interactions. One object is apparently in a late-stage merger with an AGN separation of < 5kpc, while the second is in an early-stage merger with interacting galaxies having established a tidal bridge. Both objects have dual, luminous X-ray sources that are most likely due to actively accreting massive black holes. Also, both objects have infrared counterparts, with colors consistent with being AGN. Follow-up observations will provide us a glimpse into key processes that govern the earliest phases of growth of galaxies, their central black holes, and merger-induced star formation.