On the suppression of forbidden line emission in type 1 Seyfert galaxies.

It is shown that the absence of a broad forbidden emission-line component in the spectra of Seyfert 1 galaxies almost certainly results from collisional deactivation rather than from photoexcitation and/or photoionization. The requisite high densities need not be assumed but can be inferred from the fluxes and variations of the Balmer lines. The conclusion is probably applicable to other objects which display a broad component in the permitted emission lines.