arXiv subjects
Publications and source records attributed to Glenn van de Ven.
We have developed an orbit-based method for constructing triaxial models of elliptical galaxies, which fit their observed surface brightness and kinematics. We have tested the method against analytical models with general distribution functions. Here, we present models that fit integral-field SAURON observations of NGC3379 and NGC4365.
We analyse SAURON kinematic maps of the inner kpc of the early-type (Sa) barred spiral galaxy NGC5448. The observed morphology and kinematics of the emission-line gas is patchy and perturbed, indicating clear departures from circular motion. The kinematics of the stars is more regular, and display a small inner disk-like system embedded in a large-scale rotating structure. We focus on the [OIII] gas, and use a harmonic decomposition formalism to analyse the gas velocity field. The higher-order harmonic terms and the main kinematic features of the observed data are consistent with an analytically constructed simple bar model. The bar model is derived using linear theory, considering an m=2 perturbation mode, and with bar parameters which are consistent with the large-scale bar detected via imaging. We also study optical and near infra-red images to reveal the asymmetric extinction in NGC5448, and we recognise that some of the deviations between the data and the analytical bar model may be due to these complex dust features. Our study illustrates how the harmonic decomposition formalism can be used as a powerful tool to quantify non-circular motions in observed gas velocity fields.
We have developed a method to construct realistic triaxial dynamical models for elliptical galaxies, allowing us to derive best-fitting parameters, such as the mass-to-light ratio and the black hole mass, and to study the orbital structure. We use triaxial theoretical Abel models to investigate the robustness of the method.
The Jeans equations relate the second-order velocity moments to the density and potential of a stellar system. For general three-dimensional stellar systems, there are three equations, but these are not very helpful, as they contain six independent moments. By assuming that the potential is triaxial and of separable Staeckel form, the mixed moments vanish in confocal ellipsoidal coordinates. The three Jeans equations and three remaining non-vanishing moments form a closed system of three highly-symmetric coupled first-order partial differential equations in three variables. They were first derived by Lynden-Bell in 1960, but have resisted solution by standard methods. Here we present the general solution by superposition of singular solutions.