Observing the Birth of Massive Galaxies at Cosmic Dawn and Maximizing Canada's Investment in JWST and Euclid

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Galaxies are host to the stars and planets, and are the building blocks of structure in our Universe. We are residents of the Milky Way, a relatively massive galaxy which means developing a firm understanding of how massive galaxies form and evolve is essential for understanding humankind's place in the cosmos. In the last decade enormous progress has been made in the study of galaxy formation aided in large part by advancements in near-infrared imaging and spectroscopic capabilities. These advances have allowed us to look at the most distant galaxies, which due to the finite travel time of light, act as "time machines" which show us the earliest stages of their formation directly. While we continue to learn much, there are still many basic questions we do not have the answer to: When do the very first massive galaxies form? What does that process look like? Why do massive galaxies stop forming stars? And how do massive galaxies and the supermassive black holes that live within them co-evolve?Answering these questions using ground-based data alone is becoming increasingly challenging. However, the landscape for infrared studies will change dramatically in the coming years. In October 2018, NASA will launch the James Webb Space Telescope (JWST), the 6.5m mid-infrared optimized successor to the Hubble Space Telescope (HST). Canada is a member of the JWST collaboration, having contributed key instrumentation at a cost of $150 million. A few years later in late 2020, the European Space Agency with launch Euclid, a wide-field telescope similar to the HST which will obtain Hubble-quality observations over about one-third of the night sky. Canada is also a member of the Euclid consortium via a commitment to provide ~$1.5m dollars of ground-based imaging data to support the mission. These telescopes will revolutionize our understanding of the distant universe; however, without significant investments in research before their launch, we will not be able to take full advantage of the limited lifetime of these observatories. In particular, JWST requires the pre-selection of spectroscopic targets using our best ground-based observations, and Euclid requires the optimization of data analysis algorithms. The goal of my research over the next 5 years is two-fold. Firstly, to use observations from ongoing, and recently-approved degree-scale, ground-based infrared imaging surveys such as UltraVISTA-E and VEILS to make the most comprehensive study of the growth of massive galaxies and their properties at high redshift (z > 4). Thereafter, the high-redshift, massive galaxies discovered from these datasets will be ideal targets for spectroscopic observations with JWST. Secondly, I plan to exploit recent HST observations of distant galaxy clusters to constrain the astrophysics of how environment stops galaxies from forming stars, and also use those data to validate and optimize cluster detection algorithms for Euclid.