Molecular tracers of high mass star-formation in external galaxies

TL;DR

This paper investigates how molecular tracers in star-forming regions vary with physical conditions and evolution, aiming to identify markers for different galaxy types and redshifts.

Contribution

It provides a detailed analysis of molecular abundance trends in star-forming regions under diverse physical parameters, highlighting tracers for various galaxy environments.

Findings

Certain hot core molecules are detectable in external galaxies at high redshift.

Molecular abundance trends reveal physical conditions and evolutionary stages.

Potential tracers are identified for spiral, active, low-metallicity, and high-redshift galaxies.

Abstract

Hot core molecules should be detectable in external active galaxies out to high redshift. We present here a detailed study of the chemistry of star-forming regions under physical conditions that differ significantly from those likely to be appropriate in the Milky Way Galaxy. We examine, in particular, the trends in molecular abundances as a function of time with respect to changes in the relevant physical parameters. These parameters include metallicity, dust:gas mass ratio, the H$_{2}$ formation rate, relative initial elemental abundances, the cosmic ray ionization rate, and the temperature of hot cores. These trends indicate how different tracers provide information on the physical conditions and on evolutionary age. We identify hot core tracers for several observed galaxies that are considered to represent spirals, active galaxies, low-metallicity galaxies, and high-redshift galaxies. Even in low-metallicity examples, many potential molecular tracers should be present at levels high enough to allow unresolved detection of active galaxies at high redshift containing large numbers of hot cores.