http://arxiv.org/abs/1401.4191
We map the kinematics of stars in simulated galaxy disks with spiral arms using the vertex deviation of the velocity ellipsoid. We use test particle simulations including, for the first time, fully self-consistent and high resolution N-body models. We compare our maps with the analytical predictions of the Tight-Winding Approximation (TWA) model. We see that, independently of the model, when the spiral arms are non-corotant the vertex deviation parameter values are related with the position of density peaks of overdense and underdense regions. We also find that if the spiral arms do not corotate with the disk, the sign of the vertex deviation changes from negative to positive when crossing the spiral arms in the direction of rotation, in the places where the spiral arms are in between corotation and the Outer Lindblad Resonance (OLR). By contrast, when they are inside the corotation radius and outside the Outer Lindblad Resonance, l$_v$ changes from negative to positive. We propose that measurements of the vertex deviations pattern can be used to trace the position of the main resonances of the spiral arms. For unbarred N-body simulations with corotant spiral arms our analysis suggests that no clear correlation exists between l$_v$ and density structures.
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