of Victoria
AstronomyNavigation
B.A.Sc (Toronto), PhD (Princeton)
Cosmology, theoretical and computational astrophysics, formation and evolution of galaxies, groups and clusters, AGN feedback
Observations inform us that our physical Universe emerged from the Big Bang in an exceedingly smooth and homogenous state. And yet, gazing out at the Cosmos today, we see a highly structured Universe in which matter is spun into rich web-like chains of galaxies, occasionally punctuated by massive dynamic swarms (“clusters”) of up to a thousand bright galaxies held together by their mutual gravity, all woven around giant empty voids millions of light-years across. Explaining the transition from one state to another, and understanding the chain of physical processes that endow the cosmic structures with their observed properties forms the basis of my research. The process of cosmic structure formation can, in broad strokes, be summarized as follows: The cosmic distribution of matter – most of which is “invisible” dark matter (only 14% of the matter in the universe is ordinary matter of the kind we are made of) – is initially smooth except for tiny ripples with relative amplitudes of smaller than 1 part in 105 . Gravity amplifies these ripples to form the first generation structures, which under further influence of gravity merge to form successively larger systems as the Universe ages. This simple description, however, glosses over all the complexities that lend diversity and richness to the Cosmos. The different components (radiation, gas, dark matter, galaxies, stars) can mingle, impact and in some instances, even transform from one to the other or generate the other, in myriads of ways. Discovering the weft and warp of the corresponding physical processes requires creativity, passion and sometimes sheer doggedness. It involves hunting for clues, both hidden and obvious, and cultivating insights. And, while in other areas of science, clues and insights can be had by designing an experiment and repeating it over and over under different conditions, we (humans) are hardly in a position to tweak and repeat the Big Bang, except virtually. Using some of the most powerful supercomputers in the world, we can simulate the evolution of the Universe, replicating the Universe's 13.7 billion year history in anywhere from two weeks to several months, depending on the degree of detail that we wish to capture, and in doing so, we have learnt more about the physical Universe in the past 25 years than in the preceding 10,000 years spanning nearly the entirety of human civilization.