VARIATIONS OF ELECTRON DENSITY WITHIN M8

The ratios of the brightnesses of the [O ii] lines at 3729 Å and 3726 Å were measured at 37 positions across M8. A multiple shell model was then constructed to estimate the large-scale variations of this ratio within the nebula. The amplitude and scale of the microscopic fluctuations of the electron density were then estimated by comparing these corrected [O ii] measurements with previous radio observations of the r.m.s. electron density. It is concluded that the ionized matter in M8 is condensed to within approximately 0.025 of the volume occupied by the nebula. © 1969 D. Reidel Publishing Company.