Exploring the central region of NGC 1365 in the ultraviolet domain

TL;DR

This study combines high-resolution ultraviolet and optical data to analyze star formation and AGN outflows in NGC 1365's central 5 kpc, revealing star-forming regions, outflow dynamics, and diffuse AGN-related UV emission.

Contribution

It provides new insights into the interplay between AGN activity and star formation in NGC 1365 using combined UV and optical observations.

Findings

Star formation rate in the circumnuclear ring is comparable to starbursts.

AGN outflow velocity is less than escape velocity, implying gas will rain back.

Diffuse UV emission is of AGN origin, associated with outflows.

Abstract

Active galactic nuclei (AGN) feedback and its impact on their host galaxies are critical to our understanding of galaxy evolution. Here, we present a combined analysis of new high resolution ultraviolet (UV) data from the Ultraviolet Imaging Telescope (UVIT) on AstroSat and archival optical spectroscopic data from VLT/MUSE, for the Seyfert galaxy, NGC 1365. Concentrating on the central 5 kpc region, the UVIT images in the far and near UV show bright star forming knots in the circumnuclear ring as well as a faint central source. After correcting for extinction, we found the star formation rate (SFR) surface density of the circumnuclear 2 kpc ring to be similar to other starbursts, despite the presence of an AGN outflow, as seen in [OIII] 5007 Angstrom. On the other hand, we found fainter UV and thus lower SFR in the direction south-east of the AGN relative to north-west in agreement with observations at other wavelengths from JWST and ALMA. The AGN outflow velocity is found to be lesser than the escape velocity, suggesting that the outflowing gas will rain back into the galaxy. The deep UV data has also revealed diffuse UV emission in the direction of the AGN outflow. By combining [OIII] and UV data, we found the diffuse emission to be of AGN origin.