Does the Narrow [O III] 5007 Line Reflect the Stellar Velocity   Dispersion in AGN?
  It has been proposed that the width of the narrow [O III] 5007 emission line can be used as a surrogate for the stellar velocity dispersion in active galaxies. This proposition is tested using the SDSS EDR spectra of 107 low-redshift radio-quiet QSOs and Seyfert 1 galaxies by investigating the correlation between black hole mass, as determined from H-beta FWHM and optical luminosity, and [O III] FWHM. The correlation is real, but the scatter is large. Without additional information or selection criteria, the [O III] width can predict the black hole mass to a factor of 5. 
Todd A. Boroson (NOAO)