Chemical evolution along the circumnuclear ring of M83

TL;DR

This study uses ALMA observations to analyze chemical changes in molecular clouds around M83's circumnuclear ring, revealing how gas dynamics influence star formation and molecular chemistry in galaxy centers.

Contribution

It provides the first detailed case of chemical evolution in the circumnuclear ring of a barred galaxy using high-resolution ALMA data.

Findings

Elevated shock and dense-core tracers in one orbit-intersecting area.

Peaks of CN and H41α downstream of shock regions.

Variation in chemical tracers correlates with star formation activity.

Abstract

We report an astrochemical study on the evolution of interstellar molecular clouds and consequent star formation in the center of the barred spiral galaxy M83. We used the Atacama Large Millimeter/submillimeter Array (ALMA) to image molecular species indicative of shocks (SiO, CH$_3$OH), dense cores (N$_2$H$^+$), and photodissociation regions (CN and CCH), as well as a radio recombination line (H41$\alpha$) tracing active star-forming regions. M83 has a circumnuclear gas ring that is joined at two areas by gas streams from the leading-edge gas lanes on the bar. We found elevated abundances of the shock and dense-core tracers in one of the orbit-intersecting areas, and found peaks of CN and H41$\alpha$ downstream. At the other orbit-intersection area, we found similar enhancement of the shock tracers, but less variation of other tracers, and no sign of active star formation in the stream. We propose that the observed chemical variation or lack of it is due to the presence or absence of collision-induced evolution of molecular clouds and induced star formation. This work presents the most clear case of the chemical evolution in the circumnuclear rings of barred galaxies, thanks to the ALMA resolution and sensitivity.