Correlation z_g × FWHM for LINER (solid dots) and SB/composite (empty dots) galaxies. The gravitational redshift z_g is given by the difference z_central − z_out between the redshifts of each line measured in the central and outer regions. The FWHMs are measured at the inner annulus. The line shows a fit following Eq. (1), where only the amplitude is fitted to the points, corresponding to f_fit ∼ 400.