Ionization and Star Formation in the Giant HII Region SMC-N66
  The NGC 346 young stellar system and associated N66 giant HII region in the
Small Magellanic Cloud are the nearest example of a massive star forming event
in a low metallicity ($Z\approx0.2Z_{\odot}$) galaxy. With an age of
$\lesssim$3Myr this system provides a unique opportunity to study relationships
between massive stars and their associated HII region. Using archival data, we
derive a total H$\alpha$ luminosity of
L(H$\alpha$)=4.1$\times$10$^{38}$ergs$^{-1}$ corresponding to an
H-photoionization rate of 3$\times$10$^{50}$s$^{-1}$. A comparison with a
predicted stellar ionization rate derived from the more than 50 known O-stars
in NGC 346, including massive stars recently classified from HST FUV spectra,
indicates an approximate ionization balance. Spectra obtained with SALT suggest
the ionization structure of N66 could be consistent with some leakage of
ionizing photons. Due to the low metallicity, the far ultraviolet luminosity
from NGC 346 is not confined to the interstellar cloud associated with N66.
Ionization extends through much of the spatial extent of the N66 cloud complex,
and most of the cloud mass is not ionized. The stellar mass estimated from
nebular L(H$\alpha$) appears to be lower than masses derived from the census of
resolved stars which may indicate a disconnect between the formation of high
and low mass stars in this region. We briefly discuss implications of the
properties of N66 for studies of star formation and stellar feedback in low
metallicity environments.
