Spitzer Analysis of HII Region Complexes in the Magellanic Clouds:
  Determining a Suitable Monochromatic Obscured Star Formation Indicator
  HII regions are the birth places of stars, and as such they provide the best
measure of current star formation rates (SFRs) in galaxies. The close proximity
of the Magellanic Clouds allows us to probe the nature of these star forming
regions at small spatial scales. We aim to determine the monochromatic IR band
that most accurately traces the bolometric IR flux (TIR), which can then be
used to estimate an obscured SFR. We present the spatial analysis, via
aperture/annulus photometry, of 16 LMC and 16 SMC HII region complexes using
the Spitzer IRAC and MIPS bands. UV rocket data and SHASSA H-alpha data are
also included. We find that nearly all of the LMC and SMC HII region SEDs peak
around 70um, from ~10 to ~400 pc from the central sources. As a result, the
sizes of HII regions as probed by 70um is approximately equal to the sizes as
probed by TIR (about 70 pc in radius); the radial profile of the 70um flux,
normalized by TIR, is constant at all radii (70um ~ 0.45 TIR); the 1-sigma
standard deviation of the 70um fluxes, normalized by TIR, is a lower fraction
of the mean (0.05 to 0.12 out to ~220 pc) than the normalized 8, 24, and 160um
normalized fluxes (0.12 to 0.52); and these results are invariant between the
LMC and SMC. From these results, we argue that 70um is the most suitable IR
band to use as a monochromatic obscured star formation indicator because it
most accurately reproduces the TIR of HII regions in the LMC and SMC and over
large spatial scales. We also explore the general trends of the 8, 24, 70, and
160um bands in the LMC and SMC HII region SEDs, radial surface brightness
profiles, sizes, and normalized (by TIR) radial flux profiles. We derive an
obscured SFR equation that is modified from the literature to use 70um
luminosity, SFR(Mo/yr) = 9.7(0.7)x10^{-44} L(70)(ergs/s), which is applicable
from 10 to 300 pc distance from the center of an HII region.
