|On the Role of Viscous Transport in the Oxygen Abundance Gradient over Extended Galactic Disks
This is a report Catherine Hong and I compiled during the 2010-2011 academic year under the direction of Colin McNally, as a part of the NASA Science Research Mentoring Program at the American Museum of Natural History in NYC.
Inspired by recent observations of radial abundance gradients in the extended HI disks of galaxies, we present a numerical model to address the role of viscous transport with regard to the oxygen distribution in extended galactic disks. The viscocity in our one-dimensional disk approximation is provided by turbulent motions of the interstellar medium. These motions mix oxygen and other metals throughout the gaseous component of the galaxy. Our model runs for 7-10 Gyr, with the galaxy attaining mass through infalling gas and forming stars based on the Schmidt-Kennicutt law. Through supernovae, these stars enrich their neighborhood of the galaxy with oxygen. Our model shows that viscous transport alone cannot account for the observed abundance of oxygen past the boundary of star formation in sample galaxies. These results argue in favor of the existence of another mechanism for the transport of oxygen.