2D velocity fields of simulated interacting disc galaxies

¹ Institut für Astro- und Teilchenphysik, Universität Innsbruck, Technikerstr. 25, 6020 Innsbruck, Austria e-mail: Thomas.Kronberger@uibk.ac.at
² Institut für Astrophysik, Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
³ Argelander-Institut für Astronomie, Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany

Received: 23 April 2007
Accepted: 11 July 2007

Abstract

We investigate distortions in the velocity fields of disc galaxies and their use in revealing the dynamical state of interacting galaxies at different redshifts. We model disc galaxies in combined N-body/hydrodynamic simulations. 2D velocity fields of the gas are extracted, which we place at different redshifts from to to investigate resolution effects on the properties of the velocity field. To quantify the structure of the velocity field we also perform a kinemetry analysis. If the galaxy is undisturbed we find that the rotation curve extracted from the 2D field agrees well with long-slit rotation curves. This is not true for interacting systems, as the kinematic axis is not well defined and in general does not coincide with the photometric axis of the system. For large (Milky way type) galaxies we find that distortions are still visible at intermediate redshifts but are partly smeared out. Thus a careful analysis of the velocity field is necessary before using it for a Tully-Fisher study. For small galaxies (disc scale length ~2 kpc) even strong distortions are not visible in the velocity field at with currently available angular resolution. Therefore we conclude that current distant Tully-Fisher studies cannot give reliable results for low-mass systems. Additionally we confirm the power of near-infrared integral field spectrometers in combination with adaptive optics (such as SINFONI) to study velocity fields of galaxies at high redshift ().