2008MNRAS.390..752B

The second moment of the Hβ emission line is calculated for 329 narrow-line Seyfert 1 galaxies (NLS1s) selected from the Sloan Digital Sky Survey (SDSS), which is used to calculate the central supermassive black hole (SMBH) mass of each. We find that the second moment depends strongly on the broader component of the Hβ line profile. We find that for the NLS1s requiring two Gaussians to fit the Hβ line, the mean value of the SMBH mass from the Hβ second moment is larger by about 0.50dex than that from the full width at half-maximum. Using the gas velocity dispersion of the core/narrow component of [Oiii]λ5007 to estimate the stellar velocity dispersion σ_*, the new mass makes NLS1s fall very close to the M_BH-σ_* relation for normal active galactic nuclei. By using σ_* measured directly from SDSS spectra with a simple stellar population synthesis method, we find that for NLS1s with mass lower than 10⁷M_☉, they fall only marginally below the M_BH-σ_* relation considering the large scatter in the mass calculation.