The empty ring galaxy ESO 474 - G040

TL;DR

This paper presents detailed observations of the galaxy ESO 474-G040, revealing its ring structure and suggesting it resulted from a past galaxy merger, with ongoing star formation and complex kinematics.

Contribution

It provides new spectroscopic and imaging data of ESO 474-G040, supporting the merger origin hypothesis and analyzing its kinematics, metallicity, and stellar populations.

Findings

The galaxy has a gas ring with complex kinematics.

Star formation is ongoing in the ring.

The galaxy likely resulted from a past merger of disk galaxies.

Abstract

We describe observations of the apparently empty ring galaxy ESO 474-G040 obtained with the Southern African Large Telescope (SALT). The observations, consisting of imaging, long-slit spectroscopy and Fabry-Perot mapping of the H-alpha line, allow determining the ring kinematics as well as estimating the metallicity of the ring and the stellar population composition in its various parts. We propose that the object could best be understood as being the result of a past merger of disk galaxies, which formed a gas ring that subsequently disrupted via the bead instability and is presently forming stars.