Photoionising feedback and the star formation rates in galaxies
  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.
