Velocity profiles of galaxies with claimed black holes - I. Observations of M31, M32, NGC 3115 and NGC 4594

Abstract

The presence of a massive black hole has been invoked to match the observed rotation velocities and velocity dispersions at the centres of M31, M32, NGC 3115 and NGC 4594. Here we determine stellar line-of-sight velocity profiles of these galaxies, from high spatial resolution, high S/N spectra centred on the G-band, the Mg b triplet and the Ca II IR triplet. For all spectra we determine rotation velocities, V, velocity dispersions, σ, and deviations of the velocity profiles from a Gaussian shape, as quantified by the Gauss-Hermite moments h3,..., h6. Significant deviations of the velocity profiles from a Gaussian are present in all objects. The strongest deviations are asymmetries quantified by h3 and are found primarily along the major axis. The amplitude of h3 is typically |h31