First Multi-redshift Limits on Post–Epoch of Reionization 21 cm Signal from z = 1.96–3.58 Using uGMRT
Arnab Chakraborty, Abhirup Datta, Nirupam Roy, Somnath Bharadwaj, Tirthankar Roy Choudhury, Kanan K. Datta, Srijita Pal, Madhurima Choudhury, Samir Choudhuri, Prasun Dutta, Debanjan Sarkar
Abstract
Abstract Measurement of fluctuations in diffuse H i 21 cm background radiation from the post-reionization epoch ( z ≤ 6) is a promising avenue to probe the large-scale structure of the universe and understand the evolution of galaxies. We observe the European Large Area ISO Survey-North 1 (ELAIS-N1) field at 300–500 MHz using the upgraded Giant Meterwave Radio Telescope (uGMRT) and employ the “foreground avoidance” technique to estimate the H i 21 cm power spectrum in the redshift range z = 1.96–3.58. Given the possible systematics that may remain in the data, we find the most stringent upper limits on the spherically averaged 21 cm power spectra at k ∼ 1.0 Mpc −1 are (58.87 mK) 2 , (61.49 mK) 2 , (60.89 mK) 2 , and (105.85 mK) 2 at z = 1.96, 2.19, 2.62, and 3.58, respectively. We use this to constrain the product of neutral H i mass density (Ω HI ) and H i bias ( b HI ) to the underlying dark matter density field, [Ω HI b HI ], as 0.09, 0.11, 0.12, and 0.24 at z = 1.96, 2.19, 2.62, and 3.58, respectively. To the best of our knowledge these are the first limits on the H i 21 cm power spectra at the redshift range z = 1.96–3.58 and would play a significant role to constrain the models of galaxy formation and evolution.