Efficacy of early stellar feedback in low gas surface density
  environments
  We present a suite of high resolution radiation hydrodynamic simulations of a
small patch ($1 \ {\rm kpc}^2$) of the inter-stellar medium (ISM) performed
with Arepo-RT, with the aim to quantify the efficacy of various feedback
processes like supernovae explosions (SNe), photoheating and radiation pressure
in low gas surface density galaxies ($\Sigma_{\rm gas} \simeq 10 \ {\rm
M}_\odot \ {\rm pc}^{-2}$). We show that radiation fields decrease the star
formation rate and therefore the total stellar mass formed by a factor of $\sim
2$. This increases the gas depletion timescale and brings the simulated
Kennicutt-Schmidt relation closer to the observational estimates. Radiation
feedback coupled with SNe is more efficient at driving outflows with the mass
and energy loading increasing by a factor of $\sim 10$. This increase is mainly
driven by the additional entrainment of medium density ($10^{-2} \leq n< 1 \
{\rm cm}^{-3}$), warm ($300 \ {\rm K}\leq T<8000 \ {\rm K}$) material.
Therefore including radiation fields tends to launch colder, denser and higher
mass and energy loaded outflows. This is because photoheating of the high
density gas around a newly formed star over-pressurises the region, causing it
to expand. This reduces the ambient density in which the SNe explode by a
factor of $10-100$ which in turn increases their momentum output by a factor of
$\sim 1.5-2.5$. Finally, we note that in these low gas surface density
environments, radiation fields primarily impact the ISM via photoheating and
radiation pressure has only a minimal role in regulating star formation.
