2024/10/15 by Khandakar Asif Elahi, Elahi, Khandakar Md Asif, Somnath Bharadwaj +11
Engineering · Physics and Astronomy · #Antenna Design and Optimization #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #Energy Harvesting in Wireless Networks #FOS: Physical sciences #Instrumentation and Methods for Astrophysics (astro-ph.IM) #Radio Astronomy Observations and Technology
paper · pdf · doi:10.48550/arxiv.2410.11380
openalex publication_date 2024/10/15 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Missing frequency channels pose a problem for estimating P(k_⊥,k_∥) the redshifted 21-cm power spectrum (PS) from radio-interferometric visibility data. This is particularly severe for the Murchison Widefield Array (MWA), which has a periodic pattern of missing channels that introduce spikes along k_∥. The Tracking Tapered Gridded Estimator (TTGE) overcomes this by first correlating the visibilities in the frequency domain to estimate the multi-frequency angular power spectrum (MAPS) C_ℓ(Δν) that has no missing frequency separation Δν. We perform a Fourier transform along Δν to estimate P(k_⊥,k_∥). Considering our earlier work, simulations demonstrate that the TTGE can estimate P(k_⊥,k_∥) without any artifacts due to the missing channels. However, the spikes were still found to persist for the actual data, which is foreground-dominated. The current work presents a detailed investigation considering both simulations and actual data. We find that the spikes arise due to a combination of the missing channels and the strong spectral dependence of the foregrounds. Based on this, we propose and demonstrate a technique to mitigate the spikes. Applying this, we find the values of P(k_⊥,k_∥) in the region 0.004 ≤ k_⊥ ≤ 0.048 \rm Mpc-1 and k_∥ > 0.35 \rm Mpc-1 to be consistent with zero within the expected statistical fluctuations. We obtain the 2σ upper limit of Δ\rm UL2(k)=(918.17)2 \rm mK2 at k=0.404 \rm Mpc-1 for the mean squared brightness temperature fluctuations of the z=8.2 epoch of reionization (EoR) 21-cm signal. This upper limit is from just ∼ 17 minutes of observation for a single pointing direction. We expect tighter constraints when we combine all 162 different pointing directions of the drift scan observation.