Deep multiredshift limits on Epoch of Reionisation 21 cm Power Spectra from Four Seasons of Murchison Widefield Array Observations
Abstract
We compute the sphericallyaveraged power spectrum from four seasons of data obtained for the Epoch of Reionisation (EoR) project observed with the Murchison Widefield Array (MWA). We measure the EoR power spectrum over k = 0.07  3.0 hMpc^{1} at redshifts z = 6.5  8.7. The largest aggregation of 110 hours on EoR0 highband (3,340 observations), yields a lowest measurement of (43 mK)^{2} = 1.8× 10^{3} mK^{2} at k=0.14 hMpc^{1} and z = 6.5 (2σ thermal noise plus sample variance). Using the RealTime System to calibrate and the CHIPS pipeline to estimate power spectra, we select the best observations from the central five pointings within the 20132016 observing seasons, observing three independent fields and in two frequency bands. This yields 13,591 2minute snapshots (453 hours), based on a quality assurance metric that measures ionospheric activity. We perform another cut to remove poorlycalibrated data, based on power in the foregrounddominated and EoRdominated regions of the twodimensional power spectrum, reducing the set to 12,569 observations (419 hours). These data are processed in groups of 20 observations, to retain the capacity to identify poor data, and used to analyse the evolution and structure of the data over field, frequency, and data quality. We subsequently choose the cleanest 8,935 observations (298 hours of data) to form integrated power spectra over the different fields, pointings and redshift ranges.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 February 2020
 DOI:
 10.1093/mnras/staa414
 arXiv:
 arXiv:2002.02575
 Bibcode:
 2020MNRAS.tmp..385T
 Keywords:

 cosmology;
 instrumentation: interferometers;
 methods: statistical;
 Astrophysics  Cosmology and Nongalactic Astrophysics;
 Astrophysics  Instrumentation and Methods for Astrophysics
 EPrint:
 19 pages, 29 figures, accepted for publication in Monthly Notices of the Royal Astronomical Society