Collaborative Research: A Tale of Dwarf Galaxies and Giant Galaxies: Connecting the Smallest and the Largest Galaxies to Their Dark Matter Halos

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Astronomers seek to understand how galaxies form and evolve. The luminous matter in galaxies such as our own galaxy (the Milky Way) resides within more extensive halos of dark matter. Although the nature of dark matter is still unknown, its effects due to gravity can be studied. Astronomers use simulations to predict how dark matter halos evolve. They use indirect means to infer its presence among observed galaxies. However, the relationship between these dark matter halos and their host galaxies is still uncertain. Our understanding is weakest for the very lowest mass galaxies and for the highest mass galaxies. Leauthaud and collaborators will explore both extremes in this innovative observational research program. Using a new, high resolution imaging survey, they will measure the dark matter halos for tens of thousands of galaxies. They will compare dark matter to the profiles of luminous matter. They will focus on dwarf galaxies and giant galaxies where observations are most needed. This research will lead to new insights into the relationship between dark matter and luminous matter. Outreach from this proposal will include summer training in statistical and computational methods for undergraduates as part of established programs at Princeton and UC-Santa Cruz. The Princeton program will work with the National Astronomy Consortium to recruit students from minority and underserved populations. The UC-Santa Cruz program will recruit students through Hartnell College, a neighboring Hispanic serving institution. Together these activities will broaden participation in science among historically underrepresented groups.This proposal will advance our understanding of the stellar mass ? halo mass relation that describes the relationship between ordinary matter and dark matter in galaxies. Indirect detection of dark matter will be made via weak lensing using data from the Hyper Suprime-Cam (HSC) survey on the Subaru 8.2m telescope at Mauna Kea. This project will advance the state-of-the-art for such weak lensing measurements. In addition, due to the large area of this survey, HSC will detect rare and extremely massive galaxies ( 1011.5 Msun) that lie at the heart of the largest dark matter halos. This proposal will identify tens of thousands of such massive galaxies and perform weak lensing measurements on them. It will also study large numbers of dwarf galaxies ( 109 Msun) via weak lensing. Together these studies will reveal the relationship between luminous matter and dark matter for both low and high mass galaxies. It is in these extremes of the mass range where new measurements are most needed to resolve discrepancies with theoretical models.