Revealing the dust attenuation properties on resolved scales in NGC628
  with SWIFT UVOT data
  Understanding how dust attenuation laws vary between and within galaxies is a
key question if we want to reliably measure the physical properties of galaxies
at both global and local scales. To shed new light on this question, we present
a detailed study of the slope and bump strength of the attenuation law in the
nearby spiral galaxy NGC628 at the resolved spatial scale of 325 pc. To do so,
we have modelled a broad multi-wavelength dataset from the ultraviolet (UV) to
the infrared (IR) with the state-of-the-art SED fitting code CIGALE, including
SWIFT UVOT data for which we have developed a new optimized reduction pipeline.
We find that the median dust attenuation curve of NGC628 is fairly steep, but
not as steep as the SMC curve, and has a sub-MW-type UV bump. We observe
intriguing variations within the galaxy, with regions of high $A_V$ exhibiting
a shallower attenuation curve. We argue that the flattening of the curve is due
to a dominance of absorption-over-scattering events at higher $A_V$. No trend
between the bump strength and the IRAC 8.0 micron emission was found. However,
this does not necessarily rule out PAHs as the main contributors to the UV
bump.
