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For a sample of $\sim$80 local ($0.02 \leq z \leq 0.1$) Seyfert-1 galaxieswith high-quality long-slit Keck spectra and spatially-resolvedstellar-velocity dispersion ($\sigma_{\star}$) measurements, we study theprofile of the [OIII]$\lambda$5007A emission line to test the validity of usingits width as a surrogate for $\sigma_{\star}$. Such an approach has often beenused in the literature, since it is difficult to measure $\sigma_{\star}$ fortype-1 active galactic nuclei (AGNs) due to the AGN continuum outshining thestellar-absorption lines. Fitting the [OIII] line with a single Gaussian orGauss-Hermite polynomials overestimates $\sigma_{\star}$ by 50-100%. When lineasymmetries from non-gravitational gas motion are excluded in a double Gaussianfit, the average ratio between the core [OIII] width ($\sigma_{\rm{[OIII],D}}$) and $\sigma_{\star}$ is $\sim$1, but with individual data pointsoff by up to a factor of two. The resulting black-hole-mass-$\sigma_{\rm{[OIII],D}}$ relation scatters around that of quiescent galaxies andreverberation-mapped AGNs. However, a direct comparison between$\sigma_{\star}$ and $\sigma_{\rm {[OIII],D}}$ shows no close correlation, onlythat both quantities have the same range, average and standard deviation,probably because they feel the same gravitational potential. The large scatteris likely due to the fact that line profiles are a luminosity-weighted average,dependent on the light distribution and underlying kinematic field. Within therange probed by our sample (80-260 km s$^{-1}$), our results strongly cautionagainst the use of [OIII] width as a surrogate for $\sigma_{\star}$ on anindividual basis. Even though our sample consists of radio-quiet AGNs, FIRSTradio-detected objects have, on average, a $\sim$10% larger [OIII] core width.

Studying the [OIII]$\lambda$5007A emission-line width in a sample of $\sim$80 local active galaxies: A surrogate for $\sigma_{\star}$?