Multiwavelength Studies of Galaxy Evolution

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***We live in a hierarchically organized universe. Over the past two decades, observational evidence and theoretical predictions have converged on a remarkably successful cosmological model -- cold Dark Matter with a  Dark Energy component -- that describes the formation and evolution of structure at all scales through the gravitational amalgamation of matter. The backbone of this process is  well understood, but the physics on the scales of stars, galaxies and galaxy clusters is very complex and controlled by multiple variables.   This research program seeks to understand these processes and, in particular, the processes which formed galaxies like our own Milky Way.  ***In hierarchical structure formation  small objects (with masses of a million suns - small galaxies) form first after the Big Bang and then combine over time to form the largest objects seen today (reaching masses of a million billion stars).   The act of coalescing galaxies is a violent and complex one which dramatically alters the physical state of the systems. Existing stars are redistributed, new populations of stars are produced in prodigious triggered bursts, and central supermassive black holes grow through infalling matter. Nevertheless, if we study galaxies in the universe today we see tight relationships between their properties which are indicative of underlying global processes.***For example, the mass, shape and overall age of a galaxy is dependent on its local environment.  Massive galaxies, that are elliptical and composed of old stars inhibit dense regions of the universe, with many other galaxies nearby.  Moderate mass galaxies like our own Milky Way, with on-going star formation and spiral structure live in more isolated regions.   My research program wants to understand the reasons behind trends such as these.***Because light takes a finite time to travel, we see distant galaxies  as they existed a long time ago.  We use the world's largest telescopes to observe the most distant galaxies in the universe at a much earlier stage in their formation.  By studying many galaxies at different times and in different environments we can piece together their evolutionary history. Using light emitted at different wavelengths we can measure the amount of stars a galaxy is composed of, the rate at which it is forming new stars, and whether it is growing a supermassive black hole at its center.  Its physical shape often provides clues to the processes it is experiencing - such as a major galaxy merger event.***We study large samples of galaxies in a quest to identify and understand global trends in their evolutionary phases.  Occasionally, we discover a unique object that, if studied in detail can provide a wealth of information on a particular aspect of galaxy formation.  By combining these two distinct approaches we can piece together a picture of how the rich and complex structure we see around us today was formed. *****