The Herschel revolution: unveiling the morphology of the high mass star
  formation sites N44 and N63 in the LMC
  We study the structure of the medium surrounding sites of high-mass star
formation to determine the interrelation between the HII regions and the
environment from which they were formed. The density distribution of the
surroundings is key in determining how the radiation of the newly formed stars
interacts with the surrounds in a way that allows it to be used as a star
formation tracer. We present new Herschel/SPIRE 250, 350 and 500 mum data of
LHA 120-N44 and LHA 120-N63 in the LMC. We construct average spectral energy
distributions (SEDs) for annuli centered on the IR bright part of the star
formation sites. The annuli cover ~10-~100 pc. We use a phenomenological dust
model to fit these SEDs to derive the dust column densities, characterise the
incident radiation field and the abundance of polycyclic aromatic hydrocarbon
molecules. We see a factor 5 decrease in the radiation field energy density as
a function of radial distance around N63. N44 does not show a systematic trend.
We construct a simple geometrical model to derive the 3-D density profile of
the surroundings of these two regions. Herschel/SPIRE data have proven very
efficient in deriving the dust mass distribution. We find that the radiation
field in the two sources behaves very differently. N63 is more or less
spherically symmetric and the average radiation field drops with distance. N44
shows no systematic decrease of the radiation intensity which is probably due
to the inhomogeneity of the surrounding molecular material and to the complex
distribution of several star forming clusters in the region.
