NSF-BSF: Dark-Matter Interactions at Cosmic Dawn

Decades after its discovery, dark matter remains one of the longest-standing puzzles in astrophysics. This project will use observations from the cosmic-dawn epoch, when the first galaxies formed, to advance our understanding of dark matter. Scientists at the University of Texas and Ben Gurion University in Israel will develop a theoretical framework to model the 21-cm signal of hydrogen in the presence of different dark-matter scenarios, and use it to analyze data from the Hydrogen Epoch of Reionization Array (HERA). Even before a clear detection of the 21-cm signal is reached, this proposal will deliver new insights on the interactions between dark matter and our sector during cosmic dawn. It will also further our study of velocity-induced acoustic oscillations (VAOs), and their usefulness as a unique probe of the dark sector. As part of this project, the team will provide mentoring for several graduate students and postdocs. In addition, in an effort to promote inclusion of Hispanic and Latinx students in scientific research, the team will initiate and lead a Spanish-language journal club focused on astrophysics and cosmology. This project is supported by both the National Science Foundation and the US-Israel Binational Science Foundation to further collaborations between the astrophysical communities in the two countries, Cosmological constraints on the nature of dark matter (DM) are dominated by data from either the cosmic microwave background (CMB, from z~1000) or the late Universe (z~0). By comparison, little is known about dark matter from the intermediate epoch of cosmic dawn at z~5-25. Cosmic dawn saw the first structure formation and was the time when the gas was coldest in cosmic history. As such, it is an ideal place to look for new processes that may heat up the gas, such as decaying or annihilating DM; or cool it down, such as electrically charged DM. The PIs will use 21-cm fluctuations, where foregrounds are limited to a “wedge”, to place new limits on DM that are robust to systematics and foregrounds. This includes using HERA data and the public code to be developed to thoroughly test the models suggested to explain the claimed 21-cm detection from the Experiment to Detect the Global EoR Signature (EDGES). This project will additionally develop and implement novel tools to search for other phenomenologically interesting models in data, including how they affect the amplitude and shape of VAOs at cosmic dawn. The public software suite is an important deliverable of this project, as it will interface with public Boltzmann solvers, allowing for joint analyses of 21-cm data with the CMB and large-scale structure. 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.