Unveiling the role of galactic rotation on star formation

TL;DR

This study uses numerical simulations to analyze how galactic rotation influences star formation, unifying different star formation laws and reducing scatter in their relations.

Contribution

It demonstrates that galactic rotation suppresses bi-modality in star formation laws and introduces a unified relation with reduced scatter, considering effects of line-of-sight integration.

Findings

Star formation efficiency decreases with increasing galactic angular velocity.

A unified star formation relation reduces scatter in existing laws.

Star formation efficiency follows an exponential decay with rotation rate.

Abstract

We study the star formation process at galactic scales and the role of rotation through numerical simulations of spiral and starburst galaxies using the adaptive mesh refinement code Enzo. We focus on the study of three integrated star formation laws found in the literature: the Kennicutt-Schmidt (KS) and Silk-Elmegreen (SE) laws, and the dimensionally homogeneous equation proposed by Escala (2015) $\Sigma_{\rm SFR} \propto \sqrt{G/L}\Sigma_{\rm gas}^{1.5}$. We show that using the last we take into account the effects of the integration along the line of sight and find a unique regime of star formation for both types of galaxies, suppressing the observed bi-modality of the KS law. We find that the efficiencies displayed by our simulations are anti-correlated with the angular velocity of the disk $\Omega$ for the three laws studied in this work. Finally, we show that the dimensionless efficiency of star formation is well represented by an exponentially decreasing function of $-1.9\Omega t_{\rm ff}^{\rm ini}$, where $t_{\rm ff}^{\rm ini}$ is the initial free-fall time. This leads to a unique galactic star formation relation which reduces the scatter of the bi-modal KS, SE, and Escala (2015) relations by 43%, 43%, and 35% respectively.