Building on the archives: Connecting the CN/CO intensity ratio with global galaxy properties in nearby U/LIRGs

TL;DR

This study investigates the relationship between the CN/CO intensity ratio, a dense gas tracer, and various galaxy properties in nearby U/LIRGs, revealing correlations with star formation and AGN activity.

Contribution

It introduces the use of CN/CO ratio to estimate dense gas fraction and explores its connection with galaxy properties, including star formation and X-ray emission.

Findings

Significant correlation between dense gas fraction and star formation rate.

No trend between dense gas fraction and merger stage.

Dense gas co-located with strong X-ray emission from AGN or star formation.

Abstract

We use the CN/CO intensity ratio to obtain the dense gas fraction, $f_{\text{dense}}$, for a sample of 16 Ultra-luminous and Luminous Infrared Galaxies and compare $f_{\text{dense}}$ with a suite of global galaxy properties. We find a significant correlation between $f_{\text{dense}}$ and star formation rate calculated using both infrared luminosities and radio continuum, although there is significant scatter in each relation. We find no trend between global or peak $f_{\text{dense}}$ and merger stage. We find no correlation between global $f_{\text{dense}}$ and X-ray luminosity; however, the correlation becomes significant when we measure $f_{\text{dense}}$ at the location of peak X-ray emission. Our interpretation is that the dense gas is co-localized with strong X-ray emission from an active galactic nuclei or strong central star formation.