  We present diffraction-limited (FWHM ~ 0.3arcsec) Gemini/T-ReCS mid-infrared
(MIR: N-band or narrow-band at 8.7micron) imaging of four Luminous Infrared
Galaxies (LIRGs) drawn from a representative local sample. The MIR emission in
the central few kpc is strikingly similar to that traced by Pa-alpha, and
generally consists of bright nuclear emission and several compact circumnuclear
and/or extranuclear HII regions. The central MIR emission is dominated by these
powerful HII regions, consistent with the majority of AGN in this local sample
of LIRGs contributing a minor part of the MIR emission. The luminous
circumnuclear HII regions detected in LIRGs follow the extrapolation of the
8micron vs. Pa-alpha relation found for M51 HII knots. The integrated central
3-7kpc of galaxies, however, present elevated 8micron/Pa-alpha ratios with
respect to individual HII regions, similar to the integrated values for
star-forming galaxies. Our results show that the diffuse 8micron emission, not
directly related to the ionizing stellar population, can be as luminous as that
from the resolved HII regions. Therefore, calibrations of the star formation
rate for distant galaxies should be based on the integrated 8micron emission of
nearby galaxies, not that of the HII regions alone.
