Metal-THINGS: The association and optical characterization of SNRs with HI holes in NGC 6946

TL;DR

This study investigates the relationship between supernova remnants and HI holes in NGC 6946, revealing that SNRs and star formation are concentrated at the rims of HI holes, indicating induced star formation from superbubble expansion.

Contribution

It provides new observational evidence linking SNRs, HI holes, and star formation activity using integral field spectroscopy in NGC 6946.

Findings

SNRs are concentrated at the rims of HI holes.

Star formation rate and extinction are enhanced at the rims.

Hints of increased oxygen abundance and ionization at the rims.

Abstract

NGC~6946, also known as the `Fireworks' galaxy, is an unusual galaxy that hosts a total of 225 supernova remnant (SNR) candidates, including 147 optically identified with high [SII]/Ha line ratios. In addition, this galaxy shows prominent HI holes, which were analyzed in previous studies. Indeed, the connection between SNRs and HI holes together with their physical implications in the surrounding gas is worth of attention. This paper explores the connection between the SNRs and the HI holes, including an analysis of their physical link to observational optical properties inside and around the rims of the holes, using new integral field unit (IFU) data from the Metal-THINGS survey. We present an analysis combining previously identified HI holes, SNRs candidates, and new integral field unit (IFU) data from Metal-THINGS of the spiral galaxy NGC 6946. We analyze the distributions of the oxygen abundance, star formation rate surface density, extinction, ionization, diffuse ionized gas, and the Baldwin-Phillips-Terlevich classification throughout the galaxy. By analyzing in detail the optical properties of the 121 previously identify HI holes in NGC 6946, we find that the SNRs are concentrated at the rims of the HI holes. Furthermore, our IFU data shows that the star formation rate and extinction are enhanced at the rims of the holes. To a lesser degree, the oxygen abundance and ionization parameter show hints of enhancement on the rims of the holes. Altogether, this provides evidence of induced star formation taking place at the rims of the holes, whose origin can be explained by the expansion of superbubbles created by multiple supernova explosions in large stellar clusters dozens of Myr ago.