Searching for the Origin of Double-peaked Broad Emission Lines in a Merging Galaxy with EVN

TL;DR

This study investigates the origin of double-peaked broad emission lines in a merging galaxy, using high-resolution radio observations to test the dual AGN hypothesis.

Contribution

The paper applies VLBI imaging to a merging galaxy with double-peaked lines, providing constraints on the presence of dual AGN and advancing methods for their detection.

Findings

No compact radio emission detected at 1.7 GHz

Constraints placed on the dual AGN separation

Supports alternative explanations for double-peaked lines

Abstract

The current cosmological structure formation models predict that galaxies evolve through frequent mergers. During these events, the supermassive black holes (SMBHs) residing in the centres of the galaxies shrink to the central region, while losing energy via dynamical friction. Detection of SMBHs in these galaxy mergers is straightforward if they are actively accreting matter from their surroundings as active galactic nuclei (AGN). Currently, only a few dual AGN are known. One way to identify dual AGN candidates is by detecting double-peaked emission lines in their spectra. If these are broad spectral lines, it may indicate the existence of two broad line regions associated with two AGN. 2MASS J165939.7+183436 is a merging system, where the detected double-peaked broad emission lines can be explained by a dual AGN with an estimated separation of $0.085"$. Radio emission from this object was detected in the Faint Images of the Radio Sky at Twenty-centimeters survey with a flux density of 2.6 mJy. We used the European Very Long Baseline Interferometer Network and the enhanced Multi-Element Remotely Linked Interferometer Network to image 2MASS J165939.7+183436 at 1.7 GHz. We did not detect compact radio emission from the source.