Modelling the Spectra of Galaxies

Roger Bell

Department of Astronomy, University of Maryland

Stellar evolution modelling yields tables of effective temperatures, radii and luminosities. Before they can be compared to observational data, these quantities have to be converted to absolute magnitudes and colors. Model stellar atmosphere calculations are used to do this, with the results being checked by comparison with the colors of stars of known temperatures, abundances and gravities.
The transformed isochrones are then used to model the color-magnitude diagrams and integrated spectra and colors of globular clusters and elliptical galaxies, in order to find their ages.
During this work, it was found that neutral iron contributes significantly to the continuous absorption coefficient in the solar atmosphere. The implications of this for solar mixing will be discussed briefly.