The physics of the HII regions: the photoionization equilibrium in the HII regions of M51
Gutiérrez, L.; Beckman, J. E.
Abstract
A general overview of the physical properties of the HII regions is presented here, emphasizing the various general models made to explain their structure and behaviour. The Lyman continuum effective extinction, representing a measure of the extinguished or lost fraction of the ionizing flux, is explained briefly, and the results of a study performed on this matter are presented. This study, based on a sample of about 200 HII regions of the galaxy M51 using high resolution images acquired with the HST, suggests a highly inhomogeneous structure.