Title: Radial kinematics of brightest cluster galaxies
Authors: Ilona Soechting, Susan Ilani Loubser, Anne Sansom, Patricia Sanchez-Blazquez
Abstract:
We have obtained high signal-to-noise ratio, long-slit spectra of 49 brightest cluster galaxies (BCGs) with Gemini and WHT telescopes with the primary purpose of investigating their stellar population properties. Here, we will present the full sample of galaxies, and the measurement and interpretation of the spatially resolved radial velocity and velocity dispersion profiles. We find clear rotation curves for a number of these giant galaxies. In particular, we find rapid rotation (> 100 km/s) for two BCGs, NGC6034 and NGC7768, indicating that it is unlikely that they formed through dissipationless mergers. Velocity substructure in the form of kinematically decoupled cores is detected in 15 galaxies, and the BCG data are consistent with the trend for very massive elliptical galaxies to be supported by velocity anisotropy on the anisotropy-luminosity diagram. Thus, the rotation and incidence of velocity substructure found for BCGs seem normal compared with that of their ordinary giant elliptical counterparts. However, we find the following exceptions: we confirm that BCGs follow a different Faber-Jackson relation than giant elliptical galaxies; and we find rising velocity dispersion profiles for a small number of BCGs, which are generally not found in ordinary ellipticals, and might imply a rising M/L ratio.