Environmental dependence of star formation induced by cloud collisions in a barred galaxy

TL;DR

This study improves cloud collision models by incorporating velocity dependence, demonstrating that high velocity collisions driven by gravity explain the lower star formation efficiency observed in the bars of galaxies.

Contribution

Introduces a velocity-dependent efficiency model for cloud collisions, successfully reproducing observed star formation patterns in a barred galaxy simulation.

Findings

High velocity cloud collisions reduce star formation efficiency in galaxy bars.

Velocity dependence explains differences between bar and spiral arm star formation.

Simulation matches observed star formation rates in barred galaxies.

Abstract

Cloud collision have been proposed as a way to link the small-scale star formation process with the observed global relation between the surface star formation rate and gas surface density. We suggest that this model can be improved further by allowing the productivity of such collisions to depend on the relative velocity of the two clouds. Our adjustment implements a simple step function that results in the most successful collisions being at the observed velocities for triggered star formation. By applying this to a high resolution simulation of a barred galaxy, we successfully reproduce the observational result that the star formation efficiency (SFE) in the bar is lower than that in the spiral arms. This is not possible when we use an efficiency dependent on the internal turbulence properties of the clouds. Our results suggest that high velocity collisions driven by the gravitational pull of the clouds are responsible for the low bar SFE.