Probing the 2-D kinematic structure of early-type galaxies out to 3 effective radii

Abstract

We detail an innovative new technique for measuring the 2-D velocity moments (rotation velocity, velocity dispersion and Gauss-Hermite coefficients h3 and h4) using spectra from Keck DEIMOS multi-object spectroscopic observations. The data are used to reconstruct 2-D rotation velocity maps. Here we present data for one of five early-type galaxies whose kinematics we have measured out to ∼3 effective radii (see [1]). From these data 2D kinematic maps are constructed. We show such analyses can provide significant insights into the global kinematic structure of galaxies, and, in some cases, challenge the accepted morphological classification. Our results are of particular importance to studies which attempt to classify galaxies by their kinematic structure within one effective radius, such as the recent definition of fast- and slow- rotator classes by the SAURON project.