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. Most recently, this has involved studies of carbon, nitrogen, and silicon abundances using the HST.

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. I have a current project with collaborators outside UT to use the new Hobby-Eberly telescope at McDonald Observatory to obtain spectra of emission-line galaxies at high redshifts.

One recent interest 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 gs in the different environments. A future goal of our HET project is to compare cluster and field galaxies at substantial look-back times.


February 23, 2000
Department of Astronomy
UT Austin
Austin TX 78712