2005ApJ...621..359G

We study the evolution of H II regions inside accreting hot molecular cores (HMCs). The H II regions are being pushed by a strong stellar wind from a massive young star at the center. We consider a range of pressures characteristic of HMCs. We find that thermal conductivity reduces to a thin shell the bubble of hot shocked stellar wind so that the expansion of the H II region is driven by the momentum of the stellar wind. The H II region can expand beyond the boundary of the HMC at ∼0.1 pc, in t≲5x10⁴yr. Just before reaching the HMC boundary, it has equatorial emission measures EM_eq∼3x10⁷/cm6 pc, characteristic of ultracompact H II regions. In fact, these ionized regions will evolve from hypercompact to ultracompact H II regions as they expand inside the HMC. We also study the effect of the magnitude of the thermal conductivity coefficient on the evolution of the shocked stellar wind shell and calculate its hard X-ray emission. Because of the oscillating cooling instability of the shell, the X-ray emission is variable. This work addresses the birth and evolution of H II regions inside the HMCs where massive stars are born.