High-Resolution Radiative Transfer Modelling of M33
  In this work, we characterise the contributions from both ongoing star
formation and the ambient radiation field in Local Group galaxy M33, as well as
estimate the scale of the local dust-energy balance (i.e. the scale at which
the dust is re-emitting starlight generated in that same region) in this galaxy
through high-resolution radiative transfer (RT) modelling, with defined stellar
and dust geometries. We have characterised the spectral energy distribution
(SED) of M33 from UV to sub-mm wavelengths, at a spatial scale of 100 pc. We
constructed input maps of the various stellar and dust geometries for use in
the RT modelling. By modifying our dust mix (fewer very small carbon grains and
a lower silicate-to-carbon ratio as compared to the Milky Way), we can much
better fit the sub-mm dust continuum. Using this new dust composition, we find
that we are able to well reproduce the observed SED of M33 using our adopted
model. In terms of stellar attenuation by dust, we find a reasonably strong,
broad UV bump, as well as significant systematic differences in the amount of
dust attenuation when compared to standard SED modelling. We also find
discrepancies in the residuals of the spiral arms versus the diffuse
interstellar medium (ISM), indicating a difference in properties between these
two regimes. The dust emission is dominated by heating due to the young stellar
populations at all wavelengths ($\sim$80% at 10 $\mu$m to $\sim$50% at 1 mm).
We find that the local dust-energy balance is restored at spatial scales
greater than around 1.5 kpc.
