Characterizing Low-Mass Galaxies with Spectroscopy Through Cosmic Time

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While dwarf galaxies are the least massive of all galaxies, they are also by far the most common type in the current epoch. There is compelling evidence that massive galaxies, including the Milky Way, were built up at least in part through the cannibalization of large numbers of such low mass galaxies in the early universe. Therefore, to reconstruct how a galaxy like our own Milky Way grew, we must characterize dwarf galaxies in the early universe. These young versions of today's dwarf galaxy population are also prime candidates for the sources largely responsible for ionizing the intergalactic hydrogen left over from the Big Bang, ending the universe's so-called "Dark Ages." This award will support spectroscopy from ground-based telescopes and the James Webb Space Telescope. The team of researchers will use these data to improve our understanding of galaxy formation. This award will support the PhD work of a graduate student as well as a seminar series/mentoring program for astronomy undergraduates at the PI’s home institution. Together, Multi-Unit Spectroscopic Explorer and Near Infrared Spectrometer will allow the detection and spectroscopic characterization of the faintest and youngest galaxies ever discovered at redshifts of 4-7. In particular, the team will measure chemical abundances for galaxies over a large range in mass and redshift, and study the tight correlation between a galaxy’s stellar mass and its degree of chemical enrichment, which is not well-constrained either at low masses or high redshifts. This will help inform future large-scale studies of the local universe with the 4MOST Hemisphere Survey (4HS). The team will also study the impact of short, violent bursts of star formation on the stellar mass buildup in dwarf galaxies. Finally, the James Webb Space Telescope will be used to determine the ionizing photon output from extremely young dwarf galaxies that are expected to exist just beyond the limits of traditional observational techniques. This will have implications for the contribution of low-mass galaxies to the last major phase change in the universe: cosmic Reionization.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.