New observations of emission-line intensities are presented for 32 Seyfert galaxies. On the basis of correlations among these intensities and continuum properties inferred from UBV photometry, it is concluded that class 1 Seyfert galaxies (those with broad Balmer line wings) are ionized by a strong radiative source and are not significantly reddened by dust. The intrinsic H-alpha luminosities of the nuclei are calculated and found to correspond to a range in U magnitude from -16 to -22.5 and a range in visual absolute magnitude from -16 to -22. Other properties of the nuclei do not seem to be dependent on luminosity. For class 2 Seyfert galaxies (those resembling NGC 1068), the intrinsic H-alpha luminosities after correction for dust reddening are comparable to those of class 1, but the forbidden-line luminosities are typically 30 times stronger in class 2. It is concluded that the properties of class 2 nuclei could be explained by the presence of large numbers of very hot, luminous stars substantially reddened by dust.
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Adams et al. (1975) studied this question.