Photoionising feedback and the star formation rates in galaxies

TL;DR

This study uses radiation transfer coupled with SPH simulations to assess how photoionising feedback from high-mass stars influences star formation rates and cluster growth in galaxy regions, finding a modest reduction in star formation.

Contribution

It introduces a novel framework combining Monte Carlo radiation transfer with SPH to quantify photoionising feedback effects on star formation in galaxy simulations.

Findings

PI feedback reduces stellar cluster mass accretion by ~23%

Star formation rates decrease by about 62% with PI feedback

PI feedback likely limits star formation by a factor of 2 at most

Abstract

Aims. We investigate the effects of ionising photons on accretion and stellar mass growth in a young star forming region, using a Monte Carlo radiation transfer code coupled to a smoothed particle hydrodynamics (SPH) simulation. Methods. We introduce the framework with which we correct stellar cluster masses for the effects of photoionising (PI) feedback and compare to the results of a full ionisation hydrodynamics code. Results. We present results of our simulations of star formation in the spiral arm of a disk galaxy, including the effects of photoionising radiation from high mass stars. We find that PI feedback reduces the total mass accreted onto stellar clusters by approximately 23 per cent over the course of the simulation and reduces the number of high mass clusters, as well as the maximum mass attained by a stellar cluster. Mean star formation rates (SFRs) drop from 0.042 solar masses per year in our control run to 0.032 solar masses per year after the inclusion of PI feedback with a final instantaneous SFR reduction of 62 per cent. The overall cluster mass distribution appears to be affected little by PI feedback. Conclusions. We compare our results to the observed extra-galactic Schmidt-Kennicutt relation and the observed properties of local star forming regions in the Milky Way and find that internal photoionising (PI) feedback is unlikely to reduce star formation rates by more than a factor of approximately 2 and thus may play only a minor role in regulating star formation.