Astrophysics Seminar

Detecting the redshifted 21-cm signal from the Epoch of Reionization (EoR) remains one of the most challenging problems in observational cosmology due to bright foregrounds and instrumental systematics. A key challenge for the Murchison Widefield Array (MWA) is its periodic pattern of missing frequency channels, which introduces artifacts in the estimated 21-cm power spectrum. Through a combined analysis of simulations and MWA observations, I will show that these artifacts arise from the interplay between missing channels and the intrinsic spectral structure of foregrounds, and present a mitigation strategy to suppress them. 

Applying this framework to MWA drift-scan observations at 154 MHz (redshift of 8), we obtain noise-limited upper limits on the 21-cm power spectrum. We combine multiple drift scan pointings to tighten the upper limits to approximately (98)^2 mK-squared at k = 0.156 inverse MPc, which represents the tightest upper limit from MWA at this redshift. I will further highlight some remaining challenges in these  measurements, and present a new Bayesian component-separation framework to address those. I will discuss how the new approach can enable tighter constraints from more sensitive observations MWA and future next generation instruments.