Pre-supernova feedback mechanisms drive the destruction of molecular clouds in nearby star-forming disc galaxies

TL;DR

This study uses high-resolution observations of nearby galaxies to show that early stellar feedback rapidly disperses giant molecular clouds within a few million years, significantly influencing star formation efficiency.

Contribution

It provides the first statistical measurement of GMC dispersal timescales due to early feedback mechanisms across different galactic environments.

Findings

GMCs are dispersed within ~3 Myr after high-mass star emergence.

Early feedback mechanisms are crucial in dispersing GMCs regardless of galactic environment.

Energy coupling efficiency from feedback to GMCs is only a few tens of percent.

Abstract

It is a major open question which physical processes stop the accretion of gas onto giant molecular clouds (GMCs) and limit the efficiency at which gas is converted into stars within these GMCs. While feedback from supernova explosions has been the popular feedback mechanism included in simulations of galaxy formation and evolution, `early' feedback mechanisms such as stellar winds, photoionisation and radiation pressure are expected to play an important role in dispersing the gas after the onset of star formation. These feedback processes typically take place on small scales ($\sim 10-100$ pc) and their effects have therefore been difficult to constrain in environments other than the Milky Way. We apply a novel statistical method to $\sim 1$" resolution maps of CO and Ha emission across a sample of nine nearby disc galaxies, in order to measure the time over which GMCs are dispersed by feedback from young, high-mass stars, as a function of the galactic environment. We find that GMCs are typically dispersed within $\sim$ 3 Myr after the emergence of unembedded high-mass stars, showing no significant trend with galactocentric radius. Comparison with analytical predictions demonstrates that, independently of the environment, early feedback mechanisms (particularly photoionisation and stellar winds) play a crucial role in dispersing GMCs and limiting their star formation efficiency in nearby galaxies. Finally, we show that the efficiency at which the energy injected by these early feedback mechanisms couples with the parent GMC is relatively low (a few tens of per cent), such that the vast majority of momentum and energy emitted by the young stellar populations escapes the parent GMC.