# MUSE observations of a changing-look AGN I: The re-appearance of the broad emission lines

## TL;DR

This study reports the reappearance of broad emission lines in the changing-look AGN Mrk 590 after a decade, revealing complex gas dynamics and a star-forming host galaxy with potential fueling mechanisms.

## Contribution

First detailed analysis of the host galaxy of a changing-look AGN, showing gas reservoirs, inflows, and outflows linked to the AGN's reactivation.

## Key findings

- Broad emission lines reappeared after ~10 years.
- Host galaxy has a star-forming ring and gas reservoirs close to the black hole.
- Detected nuclear gas outflow and spiral structures indicating fueling processes.

## Abstract

Optical changing-look Active Galactic Nuclei (AGN) are a class of sources that change type within a short timescale of years or decades. This change is characterised by the appearance or disappearance of broad emission lines, often associated with dramatic AGN continuum flux changes that are orders of magnitude larger than those expected from typical AGN variability. In this work we study for the first time the host galaxy of a changing-look AGN, Mrk 590, using high spatial resolution optical and near-infrared observations. We discover that after ~ 10 yr absence, the optical broad emission lines of Mrk 590 have reappeared. The AGN optical continuum flux however, is still ~ 10 times lower than that observed during the most luminous state in the 1990s. The host galaxy shows a 4.5 kpc radius star-forming ring with knots of ionised and cold molecular gas emission. Extended ionised and warm molecular gas emission are detected in the nucleus, indicating that there is a reservoir of gas as close as 60 pc from the black hole. We observe a nuclear gas spiral between radii r ~ 0.5 - 2 kpc, which has been suggested as a dynamical mechanism able to drive the necessary gas to fuel AGN. We also discover blue-shifted and high velocity dispersion [O III] emission out to a radius of 1 kpc, tracing a nuclear gas outflow. The gas dynamics in Mrk 590 suggest a complex balance between gas inflow and outflow in the nucleus of the galaxy.