The Star Formation Rate - Dense Gas Relation in the Nuclei of Nearby Galaxies

TL;DR

This study explores the link between star formation rates and dense gas in galaxy nuclei, finding evidence that the relation varies with scale and may support volumetric models of star formation.

Contribution

It provides new observational evidence on the SFR-dense gas relation in galaxy centers, supporting volumetric Schmidt law models and highlighting scale-dependent behavior.

Findings

LIR-CO (J=3-2) index similar to KS index in galaxy centers

Index flattens to linear when considering entire galaxies

Data exclude constant index at 80% confidence level

Abstract

We investigate the relationship between the star formation rate (SFR) and dense molecular gas mass in the nuclei of galaxies. To do this, we utilize the observed 850 micron luminosity as a proxy for the infrared luminosity and SFR, and correlate this with the observed CO (J=3-2) luminosity. We find tentative evidence that the LIR-CO (J=3-2) index is similar to the Kennicutt-Schmidt (KS) index (N ~ 1.5) in the central ~1.7 kpc of galaxies, and flattens to a roughly linear index when including emission from the entire galaxy. This result may imply that the volumetric Schmidt relation is the underlying driver behind the observed SFR-dense gas correlations, and provides tentative confirmation for recent numerical models. While the data exclude the possibility of a constant LIR-CO (J=3-2) index for both galaxy nuclei and global measurements at the ~80% confidence level, the considerable error bars cannot preclude alternative interpretations.