Characterization of foregrounds and systematics for sensitive radio observations

Abstract

Observation of the redshifted 21-cm signal from the epoch of reionization is a chal lenging endeavor in observational cosmology. This signal arises from a hyperfine transition in the ground state of neutral hydrogen and is detectable using radio telescopes. Since the Universe consisted principally of neutral hydrogen at the early stages, observing this signal is crucial for understanding the formation and evolution of structures in the Universe. But the target is extremely faint and prone to con tamination by orders of magnitude stronger foregrounds and systematic influences. This thesis aims to understand and characterize these foregrounds and systematics that obscure the detection of the redshifted 21-cm from the Epoch of Reionization (EoR). The studies have been done using both observations and simulations. The observed data used from GMRT is of the extragalactic deep field Lockman Hole region centered at 325 MHz. The observed frequency band (Band 3) is just higher than the lowest frequency Band-2 in the (u)GMRT (120-250 MHz) which covers the most of the redshifted Hi signal from CD/EoR. The advantage of Band 3 is that the systematics are comparatively lower and thus facilitates achieving tighter constraints on the frequency-dependent foreground characteristics. Most of the pre vious studies are either of the two categories: a) deep in sensitivity but narrow fields of view, or b) cover wide areas but shallow in sensitivity.