2025/07/07 by Gill, Sukhdeep Singh, Bharadwaj, Somnath, Elahi, Khandakar Md Asif +2 · 1 citation
#Astrophysics of Galaxies (astro-ph.GA) #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences
paper · doi:10.48550/arxiv.2507.04964
We attempt to measure the z = 8.2 Epoch of Reionization (EoR) 21-cm bispectrum (BS) using Murchison Widefield Array (MWA) 154.2~MHz data. We find that B(k1⊥, k2⊥, k3⊥, k1∥, k2∥) the 3D cylindrical BS exhibits a foreground wedge, similar to P(k1⊥,k1∥) the 21-cm cylindrical power spectrum. However, the BS foreground wedge, which depends on (k1⊥,k1∥), (k2⊥,k2∥) and (k3⊥,k3∥) the three sides of a triangle, is more complicated. Considering various foreground avoidance scenarios, we identify the region where all three sides are outside the foreground wedge as the EoR window for the 21-cm BS. However, the EoR window is contaminated by a periodic pattern of spikes that arises from the periodic pattern of missing frequency channels in the data. We evaluate the binned 3D spherical BS for triangles of all possible sizes and shapes, and present results for Δ3 the mean cube brightness temperature fluctuations. The best 2σ upper limits we obtain for the EoR 21-cm signal are Δ3\rm UL = (1.81× 103)3~mK3 at k1 = 0.008~Mpc-1 and Δ3\rm UL = (2.04× 103)3~mK3 at k1 = 0.012~Mpc-1 for equilateral and squeezed triangles, respectively. These are foreground-dominated, and are many orders of magnitude larger than the predicted EoR 21-cm signal (∼ 103 ~mK3).