N 105 in the Large Magellanic Cloud: a newly evolved H II complex

The detailed radial velocity field of the HII region N 105, in the Large Magellanic Cloud, has been obtained for the H alpha and [O III]5007 lines with a spatial sampling of 9" and spectral ones of 16 and 7 km s(-1) respectively. The line profiles present complex splitting and broadening in several places. The peculiar velocity field and morphology indicate that N 105 contains four bubble shaped nebulae, and two bright distinct quasi spherical HII regions, more or less coeval, embedded inside another large shell nebula. They are formed essentially by the action of the stellar winds of a few exciting stars, born deep inside their parental cloud. This result is deduced from the energy added to the ionized gas by the stellar winds of early type stars and from dynamical simulations combining the effects of stellar winds with those of high density gradients inside the neutral gas. The size and the morphology of the HII region are conditioned by the depth inside the natal cloud; the observed dynamic evolution of the H II region starts at the moment of blow out of the molecular cloud. The kinematics agrees with the expected results from the stellar content and from the molecular studies. The positions of masers and of an infra-red (IR) source inside N 105 and the structure of this nebula suggest that such an IR source may be the consequence of star formation triggered by the surrounding wind pressure due to the progenitors of the presently evolved stars.