# High-Resolution Radiative Transfer Modelling of M33

## TL;DR

This study uses high-resolution radiative transfer modelling to analyze the spectral energy distribution and dust-energy balance in the galaxy M33, revealing detailed dust and stellar interactions at 100 pc scales.

## Contribution

It introduces a refined dust composition model and high-resolution RT approach to accurately reproduce M33's SED and analyze dust heating and attenuation properties.

## Key findings

- Dust emission mainly heated by young stars (~80% at 10 μm)
- Dust-energy balance restored at scales >1.5 kpc
- Discrepancies in dust attenuation between spiral arms and diffuse ISM

## Abstract

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.