Before the first supernova: combined effects of HII regions and winds on molecular clouds

TL;DR

This study models how photoionization and winds from O-stars affect molecular clouds, revealing modest dynamical impacts but significant effects on cloud morphology, photon leakage, and star formation efficiency.

Contribution

It provides a combined analysis of photoionization and wind effects on molecular clouds, highlighting the limited dynamical influence but notable morphological and star formation impacts.

Findings

Winds create central cavities in low-mass clouds.

Photon leakage reduces feedback effectiveness.

Feedback decreases star formation efficiency by 10-20%.

Abstract

We model the combined effects of photoionization and momentum--driven winds from O--stars on molecular clouds spanning a parameter space of initial conditions. The dynamical effects of the winds are very modest. However, in the lower--mass clouds, they influence the morphologies of the HII regions by creating 10pc--scale central cavities.\\ The inhomogeneous structures of the model GMCs make them highly permeable to photons, ionized gas and supernova ejecta, and the leaking of ionized gas in particular strongly affects their evolution, reducing the effectiveness of feedback. Nevertheless, feedback is able to expel large fractions of the mass of the lower escape--velocity clouds. Its impact on star formation is more modest, decreasing final star formation efficiencies by 10--20$\%$, and the rate of change of the star formation efficiency per freefall time by about one third. However, the clouds still form stars substantially faster than observed GMCs.