Research on H II Regions

My work on H II regions has involved using photoionization models to aid with the analysis of emission-line spectra of H II regions (and earlier, planetary nebulae). The main goal has been the measurement of chemical abundances. I have worked on the measurement of the primordial helium abundance and on heavy element abundances in dwarf irregular galaxies.

I have a long-standing interest in chemical composition gradients across spiral galaxies and the related question of variations in chemical abundance from galaxy to galaxy. One aspect has been the the effect of cluster environment on the abundances in spiral galaxies. Two published papers have argued that the chemical abundances in the spiral galaxies in the core of the Virgo cluster have higher abundances than spirals in the cluster periphery and in the field. This may be related to differing amounts of infall of primordial gas in the different environments. Two recent papers with Paul Robertson and others have studied the relationship between gas content and chemical abundances for spiral galaxies in clusters and in the field.

July 13, 2013
Department of Astronomy
UT Austin
Austin TX 78712