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Session 82 - Spirals & Irregulars.
Display session, Friday, January 09
As part of a project to understand gas kinematics of spiral galaxies, we have analyzed high velocity resolution HI synthesis observations of the nearly face--on galaxy NGC 1232. The neutral gas distribution extends well beyond the optical extent of the galaxy. As expected, local peaks in the HI column density are associated with the spiral arms. Further, the HI column density drops precipitously near the center of the galaxy. Closed contours in the velocity field suggest either that the system is warped or that the rotation curve declines. The results of tilted--ring analyses indicate that the disk is significantly warped; the derived rotation curve suggests the presence of a large component of dark matter in this galaxy. Finally, velocity dispersions were measured by fitting Gaussians to the spectral profiles. The derived velocity dispersions are approximately constant throughout the system, with a median value of 6.6 km s^-1. In particular, there is no indication of a radial trend in the neutral gas velocity dispersion in this galaxy. In the future, the derived kinematic and dynamic parameters may be used to constrain the elemental mixing and dispersal processes of this galaxy.
Program listing for Friday