Delay Spectrum with Phase-Tracking Arrays: Extracting the HI power
  spectrum from the Epoch of Reionization
  The Detection of redshifted 21 cm emission from the epoch of reionization
(EoR) is a challenging task owing to strong foregrounds that dominate the
signal. In this paper, we propose a general method, based on the delay spectrum
approach, to extract HI power spectra that is applicable to tracking
observations using an imaging radio interferometer (Delay Spectrum with Imaging
Arrays (DSIA)). Our method is based on modelling the HI signal taking into
account the impact of wide field effects such as the $w$-term which are then
used as appropriate weights in cross-correlating the measured visibilities. Our
method is applicable to any radio interferometer that tracks a phase center and
could be utilized for arrays such as MWA, LOFAR, GMRT, PAPER and HERA. In the
literature the delay spectrum approach has been implemented for near-redundant
baselines using drift scan observations. In this paper we explore the scheme
for non-redundant tracking arrays, and this is the first application of delay
spectrum methodology to such data to extract the HI signal. We analyze 3 hours
of MWA tracking data on the EoR1 field. We present both 2-dimensional
($k_\parallel,k_\perp$) and 1-dimensional (k) power spectra from the analysis.
Our results are in agreement with the findings of other pipelines developed to
analyse the MWA EoR data.
