INTERNAL TURBULENCE, VIRIALITY, AND DENSITY BOUNDING OF THE MOST LUMINOUS-H-II REGIONS IN THE SPIRAL GALAXY-M-100

We present TAURUS Fabry-Perot velocity data in H alpha emission of the disc of the grand design spiral M 100 (NGC 4321). We have studied the emission spectra of the 200 H II regions most luminous in H alpha, ca librated in luminosity using photometric H alpha imaging from the lite rature. The emission spectra of individual H II regions were fitted us ing one or more Gaussian functions, and analyzed in terms of their vel ocity dispersion. We concentrate on the question of whether the emissi on lines show values of their internal velocity dispersions of H II re gions which would be predicted from the virial theorem, and find that in general this is not the case. There is a systematic trend to super- virial line widths, characteristic of the non-equilibrium effects of p owerful OB stellar winds, and supernovae. We propose that the lower en velope in velocity dispersion sigma, in the plot of H alpha luminosity v. sigma represents the virialized regions, and give a tentative theo retical explanation for its slope of 2.6 in the log-log plane, in term s of density bounding for the regions of highest luminosity.