The CO-H2 Conversion Factor in Galaxy Mergers

TL;DR

This paper reviews empirical and theoretical insights into how the CO-H2 conversion factor varies across different galaxy environments, especially in mergers and starbursts, and proposes a functional model for it.

Contribution

It introduces a new functional form for the CO-H2 conversion factor applicable across various scales and environments, enhancing understanding of molecular gas in galaxy mergers.

Findings

The conversion factor varies with physical environment.

A functional model for Xco is proposed.

Implications for the Kennicutt-Schmidt law are discussed.

Abstract

The CO-H2 conversion factor in galaxies is typically described as bimodal: one value for discs and quiescent regions, and another (lower) value for mergers and starbursts. In this proceeding, I will describe both empirical observational evidence that the conversion factor varies with physical environment, as well as a theoretical model which aims to understand the physical processes which drive these variations. I present a functional form for Xco which can be applied to observations ranging in scale from ~70 pc to galaxy-wide scales, and show the consequences of the application of this model to the Kennicutt-Schmidt star formation law.