Errors in Rotation Curves and Kinematic Distances

We have explored the consequences of ignoring non-circular motions in galactic orbits by performing synthetic observations of a simulated disk galaxy. We have obtained a synthetic rotation curve and estimated the errors in measured kinematic distances. The measured rotation curve had been found to have features similar to the one measured for the Milky Way Galaxy, and differs from the real rotation, i.e., the one obtained from the background potential imposed in the simulation. When the measured rotation is used to estimate distances, the error is < 0.5 kpc for most of the disk and larger at the locations of the spiral arms, therefore selectively affecting objects related to the spiral structure. The distance errors were actually larger when we used the real rotation curve. If we use kinematic distances under the assumption of circular orbits in order to reconstruct the structure of the model galaxy from the synthetic I-v map, we obtain a quite distorted picture of the galaxy. If we, instead, assume a non-circular velocity model and use it to determine distances, most of density structure in the numerical model is recovered.