Decoding the First Galaxies via 21-cm Fluctuations

The first galaxies formed from pristine hydrogen gas within the first billion years of cosmic history, but our theories cannot fully explain how. A team of scientists from the University of Texas, Austin, will tackle the questions of how the first galaxies assembled their stellar mass in the first billion years, what was their cosmological context, and what were the drivers of cosmic reionization. The team will provide mentoring for undergraduate and graduate students, as well as a postdoc. In an effort to promote scientific discussion in Hispanic and Latinx communities, the PI will partner with the McDonald Observatory in West Texas and for the first time develop one of their educational DeepSkyTour videos entirely in Spanish. The next decade will see detailed observations of the 21-cm line of neutral hydrogen, which will revolutionize our understanding of the first galaxies by probing their spatial distribution. This is key to breaking degeneracies in our theoretical models of the first cosmological structures. Extracting this information, however, requires careful and efficient modeling of the 21-cm signal beyond the spatial average. This project will provide this modeling through fast, flexible, and robust theoretical tools that will be made publicly available to the community through the Zeus21 software package. The team will implement stochastic galaxy formation on 21-cm models, study whether the reionization process was dominated by large or small bubbles, and develop new cosmological tests during reionization. This project will reveal the astrophysics sculpting the first cosmic structures, and in addition to scientific publications, talks, and public software releases, it will provide ultra-efficient 21-cm map-making techniques for both educational and scientific purposes. 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.