Optimal estimates of line-of-sight velocity distributions from absorption line spectra of galaxies - Nuclear discs in elliptical galaxies

Rix, H.W. & White, S.D.M. 1992, M.N.R.A.S. 254, 389.

Methods for extracting line-of sight velocity distributions (LOSVDs) from the broadening of absorption lines in early-type galaxies are presented. These methods operate exclusively in pixel space, they use the full information content of the data, they permit a rigorous treatment of the errors, and they relax the standard a priori assumption that the LOSVD is a Gaussian. Attention is given to two problems: optimal noise filtering for model-independent extraction of the LOSVD, subject only to the constraint that it be bandwidth-limited; and optimal parameter estimation when the LOSVD can be assumed to belong to the parameterized family of models, e.g., single or double Gaussians. These methods are applied to two elliptical galaxies with kinematically distinct cores (NGC 5322 and NGC 3610), and LOSVDs are found which deviate significantly from a Gaussian.