NGC 6744 - A nearby Milky Way twin with a very low-luminosity AGN

TL;DR

NGC 6744, a galaxy similar to the Milky Way, hosts a low-luminosity AGN with complex nuclear and circumnuclear regions, revealing past activity and a gaseous disk misaligned with the stellar disk.

Contribution

This study provides detailed analysis of NGC 6744's nuclear activity, including evidence of a past more luminous AGN and the discovery of a misaligned gaseous disk.

Findings

Detection of a low-luminosity AGN with LINER features

Identification of a gaseous rotating disk misaligned with the stellar disk

Evidence suggesting a past merger event about one billion years ago

Abstract

NGC 6744 is the nearest and brightest south-hemisphere galaxy with a morphological type similar to that of the Milky Way. Using data obtained with the Integral Field Unit of the Gemini South Multi-Object Spectrograph, we found that this galaxy has a nucleus with LINER (Low Ionization Nuclear Emission Line Region) surrounded by three line emitting regions. The analysis of the Hubble Space Telescope archival images revealed that the nucleus is associated with a blue compact source, probably corresponding to the active galactic nucleus (AGN). The circumnuclear emission seems to be part of the extended narrow line region of the AGN. One of these regions, located $\sim$1" southeast of the nucleus, seems to be associated with the ionization cone of the AGN. The other two regions are located $\sim$1" south and $\sim$0.6" northeast of the nucleus and are not aligned with the gaseous rotating disk. Spectral synthesis shows evidence that this galaxy may have gone through a merger about one billion years ago. On the basis of the kinematic behavior, we found a gaseous rotating disk, not co-aligned with the stellar disk. Given the relative degree of ionization and luminosities of the nuclear and circumnuclear regions, we suggest that the AGN was more luminous in the past and that the current circumnuclear emissions are echoes of that phase.