Description
- Abstract:
- We have yet to observe the universe between the Cosmic Microwave Background (CMB) at z~1100 and the first galaxies at z~14, a period known as the Cosmic Dark Ages, when the universe was largely neutral Hydrogen and Dark Matter interacting gravitationally. Despite the lack of luminous sources during the aptly named Dark Ages, there does exist an observable signal thanks to the quantum mechanical Hyperfine transition of neutral Hydrogen: the 21 cm line. It is well understood that observation of this signal has the potential to offer greater constraints than the CMB in the cosmic variance limit, a probe of inflationary perturbations, and a window into exotic physics models. However, the 21 cm signal is highly red-shifted to problematic frequencies (1-50 MHz) that have significant overlap with artificial sources of Radio Frequency Interference (RFI) and with regions of opacity in the Earth's ionosphere. As a result, radio experiments to observe the Dark Ages have set their sights on the far side of the Moon which shields from Earth-based RFI and lacks an ionosphere. Of course, constructing a radio telescope on the Moon is no easy picture, so it is paramount to forecast and simulate various instrument configurations before committing to an experiment. In this work, I present high-precision simulations of Lunar interferometric array concepts to examine two important hurdles: obtaining a high signal-to-noise ratio (SNR) in the presence of bright thermal noise and quantifying the extent of diffuse foreground contamination in 21 cm power spectrum measurements. Regarding the former, I present an update to the FarView configuration, as presented in Advances in Space Research, in order to achieve a 10 σ detection of the z=30 21 cm power spectrum with a ~100,000 dipole array in the absence of foregrounds. For the latter hurdle, I show that complex spectral structure arises from the coupling of one's instrument with the lunar regolith. Overall, I argue that these results necessitate that one be able to precisely model the electromagnetic response of one's antennas in order to measure the 21 cm power spectrum.
- Notes:
- Thesis (Ph. D.)--Brown University, 2026
Citation
Smith, Willow,
"Achieving a Detection of the 21 cm Signal of the Cosmic Dark Ages: Simulation and Forecasting of a Lunar Far Side Radio Array"
(2026).
Physics Theses and Dissertations.
Brown Digital Repository. Brown University Library.
https://repository.library.brown.edu/studio/item/bdr:zq3zr8cb/
