2002ApJ...576L..15T

We present an iteration method to derive exact rotation curves (RCs) of spiral galaxies from observed position-velocity (PV) diagrams that comprises the following procedure. An initial RC (RC0) is adopted from an observed PV diagram (PV0) obtained by any simple method, such as the peak-intensity method. Using this RC and an observed radial distribution of intensity (emissivity), we construct a simulated PV diagram (PV1). The difference between an RC obtained from PV1 and the original RC (e.g., difference between peak-intensity velocities) is used to correct the initial RC to obtain a corrected rotation curve, RC1. This RC1 is used to calculate another PV diagram (PV2) using the observed intensity distribution and to obtain the second iterated RC (RC2). This iteration is repeated until PVi converges to PV0 so that the difference between PVi and PV0 becomes minimal. Finally, RCi is adopted as the most reliable RC. We apply this method to some observed PV diagrams of nearby galaxies and show that the iteration successfully converges to give reliable RCs. We show that the method is powerful in detecting central massive objects.