HNCO abundances in galaxies: Tracing the evolutionary state of starbursts

TL;DR

This study investigates molecular tracers in galaxy nuclei, revealing that HNCO abundance variations effectively indicate the evolutionary stage of nuclear starbursts, with implications for understanding galactic activity.

Contribution

It demonstrates that HNCO abundance variations serve as a diagnostic tool for the evolutionary state of starbursts in galaxy nuclei, based on multi-line molecular observations.

Findings

HNCO abundance varies by nearly two orders of magnitude among galaxies.

C32S and C34S are not significantly affected by activity type.

HNCO is a good tracer of molecular fueling in starbursts.

Abstract

The chemistry in the central regions of galaxies is expected to be strongly influenced by their nuclear activity. To find the best tracers of nuclear activity is of key importance to understand the processes taking place in the most obscured regions of galactic nuclei. In this work we present multi-line observations of CS, C34S, HNCO and C18O in a sample of 11 bright galaxies prototypical for different types of activity. The 32S/34S isotopic ratio is ~10, supporting the idea of an isotopical 34S enrichment due to massive star formation in the nuclear regions of galaxies. Although C32S and C34S do not seem to be significantly affected by the activity type, the HNCO abundance appears highly contrasted among starburst. We observed HNCO abundance variations of nearly two orders of magnitude. The HNCO molecule is shown to be a good tracer of the amount of molecular material fueling the starburst and therefore can be used as a diagnostics of the evolutionary state of a nuclear starburst.