Extinction and PAH intensity variations across the HII region IRAS
  12063-6259
  The spatial variations in PAH band intensities are normally attributed to the
physical conditions of the emitting PAHs, however in recent years it has been
suggested that such variations are caused mainly by extinction. To resolve this
question, we have obtained near-infrared (NIR), mid-infrared (MIR) and radio
observations of the compact H ii region IRAS 12063-6259. We use these data to
construct multiple independent extinction maps and also to measure the main PAH
features (6.2, 7.7, 8.6 and 11.2 {\mu}m) in the MIR. Three extinction maps are
derived: the first using the NIR hydrogen lines and case B recombination
theory; the second combining the NIR data with radio data; and the third making
use of the Spitzer/IRS MIR observations to measure the 9.8 {\mu}m silicate
absorption feature using the Spoon method and PAHFIT (as the depth of this
feature can be related to overall extinction). The silicate absorption over the
bright, southern component of IRAS 12063-6259 is almost absent while the other
methods find significant extinction. While such breakdowns of the relationship
between the NIR extinction and the 9.8 {\mu}m absorption have been observed in
molecular clouds, they have never been observed for HII regions. We then
compare the PAH intensity variations in the Spitzer/IRS data after dereddening
to those found in the original data. It was found that in most cases, the PAH
band intensity variations persist even after dereddening, implying that
extinction is not the main cause of the PAH band intensity variations.
