Probing Cosmic Dawn with End-to-End Forward Models

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Direct observations of neutral hydrogen remain the most promising probes of "Cosmic Dawn". This project will combine state-of-the-art observations from two US-led experiments: the global Experiment to Detect the Global Epoch of Reionization (EoR) Signal (EDGES), and the interferometric Hydrogen Epoch of Reionization Array (HERA). The analysis of HERA data will discriminate between exotic explanations of EDGES’ results, including early radio-loud black holes and novel dark matter candidates beyond the standard model. On a broader level, the proposed project will deliver a common framework for combining different datasets focusing on Cosmic Dawn, increasing both the reliability and power of physical interpretations. This project will take place at a university that has a strong commitment to serving students from non-traditional backgrounds such as returning, first generation, and veteran students and will involve students in the successful Research Experiences for Non-Traditional Undergraduates program.The epoch of Cosmic Dawn, spanning a redshift of 12 to 30, encompasses the gravitational collapse of dark matter halos and the birth of the first stars and galaxies, and has far-reaching implications for both galaxy evolution and cosmology. Focusing on frequencies of 50-100 MHz – within which the first evidence for the first stars has been reported by EDGES, this program will implement a fundamentally new paradigm to account for systematics by defining modular end-to-end statistical forward models. Such forward models are the only rigorous way to account for systematic residuals and their effect on posterior constraints of astrophysics and cosmology. These forward models will be applied – both in isolation, and jointly – to forthcoming data from the third-generation EDGES experiment and the first data from the completed HERA Phase II array, yielding the most stringent physical inference to date during this epoch.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.