Looking Out for the Little Guy: A Comprehensive Study of Star Formation in Dwarf Galaxies

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In 2010, the Large Synoptic Survey Telescope (LSST) was named the top-ranked ground-based astronomy project for the coming decade. The telescope will begin gathering light in 2019, and begin a full survey of the visible sky two years later. The survey will discover billions of new astronomical objects, including hundreds of new galaxies nearby to our own Milky Way galaxy. The new galaxies that we will discover are so faint that they could not be found by previous telescopes. These tiny galaxies are also ideal places to test fundamental questions about the origin of galaxies in our Universe. This research focuses on the fact that these tiny galaxies are very sensitive to the first stars that formed in our Universe. This fact has not been sufficiently explored in previous research. To prepare astronomers to understand what these galaxies tell us about the origins of our Universe, this research focuses on three key areas. First, they will predict the number of faint galaxies that the National Science Foundation's LSST should discover. Second, they will predict how far away from the Milky Way the LSST might find the faint galaxies. Third, they will predict whether any of these galaxies is still forming stars today, or whether they all stopped forming stars billions of years ago. The research advances the scientific leadership of the United States and help to safeguard the United States' investment in LSST. The project focuses on training students who are first-generation college students, with the goal of diversifying the US technical workforce. An expanded and diversified scientific workforce helps to ensure that the US remains a leader in innovation and economic growth.The LSST will revolutionize our knowledge of dwarf galaxies, especially in the ultra-faint regime. However, simulators have barely begun to extend their successful models to stellar masses below 1 million solar masses. Now is the critical time to understand whether our current simulations can continue to explain galaxy formation down into the ultra-faint range, or whether a new understanding of star formation in low mass dark matter halos will be required. The goal of this work is to gain substantial knowledge about the processes that control early star formation in dwarf galaxies and subsequent quenching. The number of observed galaxies with stellar masses below 10 thousand solar masses depends strongly on the density of gas from which the first stars could form in the early Universe. The proposed work will generate hundreds of simulated dwarf galaxies, with stellar masses ranging from one billion solar masses (roughly 1/10 the mass of the Milky Way) down to 1000 solar masses in the range of ultra-faint dwarf galaxies. This work utilizes the simulations to (1) pinpoint the role of star formation density threshold on the number of galaxies that form, and the resulting stellar mass function; (2) make predictions for the number of ultra-faint dwarf galaxies as function of radius from the Milky Way; (3) study the processes that quench dwarf galaxies as function of mass and environment, and make predictions for the quenched fraction in the field that can be observed by future facilities. This work also establishes a program to support and mentor first-generation college students (many of whom are likely to also be from groups historically underrepresented in STEM) as they transition to being undergraduates. The program will (1) develop a mentoring relationship between students and members of the Rutgers Physics & Astronomy department, (2) utilize cohort building activities to develop the students into a peer support network for each other, (3) introduce the students to basic research tools and get them involved in original research. These three goals have been shown to increase the retention of underrepresented students in science. The overall aim is to improve the demographic diversity of both the Rutgers Physics & Astronomy undergraduate majors, but also of the Physics and Astronomy community. This program will also train graduate students to teach and mentor the first-year students, and educate the graduate student mentors on issues of equity and barriers to education that first-year/underrepresented students face.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.