Marshall L. McCall
Professor of Astronomy
Astronomy and Astrophysics
Formation and evolution of galaxies and galaxy aggregates.
How galaxies formed and how they have evolved since are subjects at the frontier of research in modern astronomy. They are relevant because of their importance to understanding our own origins, but challenging because of the great diversity of knowledge which must be pooled to address the fundamental problems.
Using data we acquire with telescopes around the world and in space, my students and I blend observation with theory to figure out what actually happened. To study evolution, we focus on measuring the properties of galaxies in the near universe. We use gaseous nebulae, specifically HII regions and planetary nebulae, to probe how stellar birth and death rates and the chemical state of matter vary from place to place within a galaxy and from galaxy to galaxy. By linking these variations to properties of individual galaxies as well as to their environment, it is possible to pin down the key physics which has affected the evolution of galaxies since formation.
The best way to study the origin of galaxies is to examine the most distant objects detectable, because the time required for light to reach us is so long that we view them as they existed just after they formed. We are developing and applying techniques to identify primeval galaxies, to determine not only how galaxies formed, but when.
How the Milky Way came to be where it is today is another subject of investigation. Dynamical simulations of the motion of the Milky Way relative to its neighbours are carried out to evaluate its path through space since the Big Bang. Besides helping to pin down the reason why we are falling towards the Andromeda galaxy, constraints on the age of the universe and the total mass of the Milky Way, dark and light, follow. The work has required detailed study of the local organization of galaxies, especially elucidation of the structure of the Local Sheet, as well as the development of a coherent system of weighing galaxies to pin down the relative masses needed for the simulations.