Collaborative Research: The Merian Survey. Characterizing Dark Matter and Feedback in Star Forming Dwarf Galaxies

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While most of the mass in the universe is unseen, the smallest galaxies in the universe (the so-called dwarf galaxies) pose significant challenges to this “dark matter” model. In order to further test our best dark matter models, a large observational survey of dwarf galaxies is needed. This project focuses on the Meriam survey, which will observe 100,000 dwarf galaxies with known distances. Furthermore, each of the dwarf galaxies in this survey has constraints on their dark matter content from other methods. The new data will provide their stellar structure and colors. These results can all be taken together to test our ideas of dark matter in the universe. The team will place priority on recruiting a diverse group of students who will carry out the data mining that will be required in the era of the Vera Rubin Observatory. Established programs at both Princeton and UC Santa Cruz recruit historically underserved students for summer research and then continuing cohort support. These students will be trained in "big-data'' and modern science analysis with Merian. Extensive studies of dwarf galaxies have revealed a considerable scatter in many of their fundamental properties. In particular, galaxies with stellar mass of 108 - 109 Msun present a diversity of star formation rates and rotation-curve shapes which are in tension with theoretical models. Reliably characterizing the dark matter distribution and baryonic processes in these galaxies, such as feedback, is key to in order to establish a complete picture of dark matter on small scales. The Merian survey will obtain a volume-limited census of dwarf galaxies in this mass range at z=0.058-0.1. Using two custom made filters, Merian will provide redshifts to a complete sample of 100,000 star forming dwarf galaxies (two orders of magnitude larger than SDSS+GAMA) over an area of 870 deg2. Combined with deep+high spatial resolution imaging from the Hyper-Suprime Camera, this program will result in high S/N weak lensing profile measurements for dwarf galaxies, probing their dark matter halos out to their virial radii. Also, Hyper-Suprime Camera imaging will be used to measure dwarf sizes and shapes. The next generation of scientists must be trained to deal with the deluge of Vera Rubin Observatory data coming in the next decade. Programs at both Princeton and UC Santa Cruz recruit historically underserved students for summer research and then continuing cohort support.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.