Astrophysical Constraints on Cosmic Dark Ages and Cosmic Dawn for Lunar Experiment

The study of the epoch of Cosmic Dark Ages and the Cosmic Dawn, corresponding to before and after the emergence of the first stars in our cosmos, offers significant insights into the early universe’s evolution, including formation of the first luminous structures or Population III stars, as well as appearance of large-scale galaxies and galaxy clusters. The sky-averaged 21-cm hydrogen line corresponding to the change in energy state of a hydrogen atom via a spin-flip transition, where the electron spin is opposite to the proton spin, provides a crucial tool for this research. The 21-cm signal allows for the penetration of interstellar and intergalactic dust clouds that would have otherwise been opaque to visible light. This 21-cm line is the only way to probe cosmological dark ages from the stages of Recombination—when protons captured electrons to form the first hydrogen atoms—to Reionization. This research investigates the astrophysical constraints on the 21-cm signal claimed to be observed by the Experiment to Detect the Global Epoch of Reionization Signature (EDGES) array, as well as using preliminary data for the upcoming Farside Array for Radio Science Investigations of the Dark Ages and Exoplanets (FARSIDE) probe to be placed on the lunar surface. By analyzing these relevant data and studying signals associated with large-scale structure of the early universe during the Cosmic Dark Ages, Cosmic Dawn and Epoch of Reionization, we aim to ultimately derive constraints on the thermal and ionization history of the intergalactic medium (IGM), the properties of the first stars and galaxies, and the nature of dark matter. This research provides the foundation for a FARSIDE pathfinder probe, including error tolerance limits on such an endeavor. Our conclusions highlight the potential of the final FARSIDE array to improve our understanding of these formative cosmic epochs.