Department of Physics & Astronomy
University of New Mexico

Center for Astrophysics Research and Technologies Seminar Series

Searching for the Global 21 cm Cosmic Dawn Absorption Signal with the Long Wavelength Array

Presented by Chris DiLullo (UNM)

The detection of the formation of the first stars and galaxies, known as Cosmic Dawn, remains one of the final frontiers in observational cosmology. As these first luminous sources begin to form, their emission drastically changes the Universe driving it from a primarily neutral state to an almost entirely ionized one throughout a period known as the Epoch of Reionization (EoR). A major science goal of the upcoming James Webb Space Telescope is the direct imaging of the first galaxies in the infrared; however, it will be limited in its ability to probe the entire EoR. The redshifted 21 cm signal from neutral hydrogen present during Cosmic Dawn and the EoR is one of the strongest observational probes of the first stars and galaxies as it traces the ionization history of the Universe. The global 21 cm Cosmic Dawn signal is expected to manifest as a small absorption feature relative to the Cosmic Microwave Background over large angles on the sky at frequencies below 100 MHz. A potential detection of this absorption signal was reported by the Experiment to Detect the Global EoR Signature (EDGES) collaboration (Bowman et al 2018) with unexpected spectral shape and amplitude. If validated, this detection could imply either new dark matter physics or a deficit in models of the early Universe. I will present efforts to validate the EDGES result using the Long Wavelength Array station located on the Sevilleta National Wildlife Refuge in New Mexico (LWA-SV). LWA-SV offers beamforming capabilities which should help with rejection of Galactic foregrounds which obscure the small cosmological signal. These efforts include the development of an achromatic beamforming framework which has been successfully deployed at LWA-SV. I will end by discussing major challenges which currently stand in the way of validation and look towards future work which will hopefully improve current limits.

2:00 pm, Thursday, June 24, 2021

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