I am primarily interested in cosmology and galaxy formation and evolution using both observational and theoretical approaches. Recently I was one of the leaders of the Supernova Legacy Survey which found that the dark energy was constant in time to a precision of better than 10%, consistent with Einstein’s cosmological constant. I am also interested in star streams as indicators of the dark matter substructure of the Milky Way halo. I was the Thirty Meter Telescope’s Canadian Project Director 2003-17.
Professor, Emeritus, UTMMeasurement of stellar spectral energy distributions, observations of stellar convection, high resolution stellar spectroscopy, models of stellar atmospheres.Ph.D. 1972, Chicago
I study the physics in stellar atmospheres. The physics is intriguing because the conditions, which cannot be recreated in our labs, are changing extremely rapidly between the dense stellar interior and the near vacuum of space. However, we have the great advantage of being able to observe directly the brightness and spectrum of the stellar atmosphere. A recent revolutionary observational development is the technique of optical/infrared interferometry that resolves the surfaces of the nearer stars. My approach concentrates on the bright stars that can be observed in the greatest detail, and to interpret those observations using computer models
Development and operation of instruments for small satellites such as BRITE Constellation. Properties and evolution of contact binary stars. Techniques for accurate computation of light curves and spectral line profiles of close binary stars, including previously neglected numerical and relativistic effects. Spectroscopy of late-type stars, their rotation and variation
I use variable stars to study the nature and evolution of stars. My current interest centers on
pulsating red giants and supergiants, which represent the semi-final stages of stars’ lives, and are poorly-understood, compared with other variable star types. I use archival data, especially from the
American Association of Variable Star Observers (AAVSO), which stretches back for a century or more, edit the Journal of the AAVSO, and otherwise facilitate the contributions of skilled amateurs to
variable star research. I am also engaged in a wide variety of astronomy education and outreach projects.
My research focuses on many aspects of high-redshift galaxy clusters. I am involved in a number of large optical/IR imaging surveys to create large samples of clusters up to redshift of 2. These provide cluster samples for projects in galaxy and cluster evolution and observational cosmology. These include spectroscopic surveys of cluster galaxies, the evolution and formation of clusters, the roles of environments in the evolution of galaxies, the morphology of galaxies in clusters, gravitational lensing, and the applications of galaxy clusters to cosmology. I also work on photometric redshift
techniques, and their applications to galaxy evolution studies involving large galaxy photometric catalogues.