  Massive stars are expected to produce wind-blown bubbles in the interstellar
medium; however, ring nebulae, suggesting the existence of bubbles, are rarely
seen around main-sequence O stars. To search for wind-blown bubbles around
main-sequence O stars, we have obtained high-resolution Hubble Space Telescope
WFPC2 images and high-dispersion echelle spectra of two pristine HII regions,
N11B and N180B, in the Large Magellanic Cloud. These HII regions are ionized by
OB associations that still contain O3 stars, suggesting that the HII regions
are young and have not hosted any supernova explosions. Our observations show
that wind-blown bubbles in these HII regions can be detected kinematically but
not morphologically because their expansion velocities are comparable to or
only slightly higher than the isothermal sound velocity in the HII regions.
Bubbles are detected around concentrations of massive stars, individual O
stars, and even an evolved red supergiant (a fossil bubble). Comparisons
between the observed bubble dynamics and model predictions show a large
discrepancy (1--2 orders of magnitude) between the stellar wind luminosity
derived from bubble observations and models and that derived from observations
of stellar winds. The number and distribution of bubbles in N11B differ from
those in N180B, which can be explained by the difference in the richness of
stellar content between these two HII regions. Most of the bubbles observed in
N11B and N180B show a blister-structure, indicating that the stars were formed
on the surfaces of dense clouds. Numerous small dust clouds, similar to Bok
globules or elephant trunks, are detected in these HII regions and at least one
of them hosts on-going star formation.
