Density studies of giant extragalactic HII regions

We have studied the variation of the electron density with position in a selected group of bright giant extragalactic HII regions with the use of long slit spectrophotometry at high spectral and spatial resolution. Density values for the ionized gas of the regions have been obtained from the measurement of the [SII] λλ6717, 6731 ratio. We conclude that the regions are not homogeneous; the density varies with position, with the zones of high density frequently associated to high surface brightness.