The Formation and Evolution of Galaxies in the Early Universe

Cosmologists have long sought to trace the history of the universe from its origins to the present day. Our earliest picture of the universe has been secured through the study of the cosmic microwave background which provides a portrait of the universe when it was just 400,000 years old. It was at this time that hydrogen, the most abundant chemical element in the present-day, first came to be. The universe that existed at these times was unlike anything we know of today. With not a single star in all of space, the cosmos was shrouded in darkness. The ordinary matter that today comprises the stars, planets, and life we see around us was almost entirely contained in a gas of hydrogen. The next available picture comes almost one billion years later in cosmic history revealing light from individual galaxies, some already containing a mass ten billion times the mass of our Sun. The hydrogen that filled so much of the universe at the time of our last picture is no longer present. Instead, the space between galaxies is filled with a sea of electrons and protons. The gap between these two epochs represents the final uncharted frontier of cosmology. Buried in this unexplored era are the keys to understanding how the first stars and galaxies came to be. It is the goal of my research to fill in this crucial missing chapter in the history of the cosmos. There are three fundamental questions that astronomers hope to address: 1) At what point over the first billion years did the first stars and galaxies emerge? 2) What destroyed the hydrogen atoms that used to permeate the space between the galaxies and when did this occur? 3) How did the large galaxies that we observe just one billion years assemble their mass? Recently I have made progress in answering some of these questions. Using the twin Keck telescopes in Hawaii, I identified the light from six galaxies which appear to be from when the universe was just 500 million years old. If true, it would indicate that young galaxies from this era produce enough radiant energy to break apart hydrogen atoms between galaxies. However, verifying that these galaxies are indeed from these very early times has proved difficult with the Keck telescopes. In contrast, with the unique instrumentation of the Very Large Telescope (VLT) in Chile, confirmation should be fairly simple. If the VLT proves that the galaxies are indeed at such great distances, then we can begin to test whether they correspond to the first generation of luminous objects. Furthermore, I plan to use new technology on the VLT and on the Hubble Space Telescope (HST) that allows larger images of the 500 million year old universe to be captured. These new pictures should provide us with a much improved understanding of the contents of the young universe. Finally, I plan to study the growth of the large galaxies seen between one and two billion years after the big bang. By using observations from HST, the Spitzer Space Telescope, the VLT, and the Keck telescopes, I can determine when the largest galaxies formed and whether they were built up from many smaller systems, as suggested by current theoretical models. Each of the projects I have described here take us forward in our pursuit of filling in the last missing chapter of cosmic history. With the constant development of new instrumentation and telescopes, I am optimistic that we will soon reach our goal.