# Kennicutt-Schmidt relation variety and star-forming cloud fraction

## TL;DR

This study explores how the Kennicutt-Schmidt relation's slope and normalization vary with the molecular gas properties and star formation efficiency across different galaxies, revealing that cloud formation efficiency influences the relation's diversity.

## Contribution

It demonstrates that variations in the R31 ratio and star formation efficiency are key factors causing the diversity in the Kennicutt-Schmidt relation among and within galaxies.

## Key findings

- Higher R31 correlates with increased star-formation efficiency.
- Different R31-Sigma_gas distributions lead to linear or super-linear KS slopes.
- Galaxies with prominent structures tend to have larger R31 and Sigma_gas.

## Abstract

The observationally derived Kennicutt-Schmidt (KS) relation slopes differ from study to study, ranging from sub-linear to super-linear. We investigate the KS-relation variety (slope and normalization) as a function of integrated intensity ratio, R31=CO(J=3-2)/CO(J=1-0) using spatially resolved CO(J=1-0), CO(J=3-2), HI, Ha and 24um data of three nearby spiral galaxies (NGC3627, NGC5055 and M83). We find that (1) the slopes for each subsample with a fixed R31 are shallower but the slope for all datasets combined becomes steeper, (2) normalizations for high R31 subsamples tend to be high, (3) R31 correlates with star-formation efficiency, thus the KS relation depends on the distribution in R31-Sigma_gas space of the samples: no Sigma_gas dependence of R31 results in a linear slope of the KS relation whereas a positive correlation between Sigma_gas and R31 results in a super-linear slope of the KS relation, and (4) R31-Sigma_gas distributions are different from galaxy to galaxy and within a galaxy: galaxies with prominent galactic structure tend to have large R31 and Sigma_gas. Our results suggest that the formation efficiency of star-forming cloud from molecular gas is different among galaxies as well as within a galaxy and is one of the key factors inducing the variety in galactic KS relation.