scholarly journals Overcoming real-world obstacles in 21 cm power spectrum estimation: A method demonstration and results from early Murchison Widefield Array data

2014 ◽  
Vol 89 (2) ◽  
Author(s):  
Joshua S. Dillon ◽  
Adrian Liu ◽  
Christopher L. Williams ◽  
Jacqueline N. Hewitt ◽  
Max Tegmark ◽  
...  
Keyword(s):  
Power Spectrum ◽  
Real World ◽  
Spectrum Estimation ◽  
Power Spectrum Estimation ◽  
Array Data ◽  
Murchison Widefield Array

scholarly journals Calibration and 21-cm power spectrum estimation in the presence of antenna beam variations

2019 ◽  
Vol 492 (2) ◽  
pp. 2017-2028 ◽  
Author(s):  
Ronniy C Joseph ◽  
C M Trott ◽  
R B Wayth ◽  
A Nasirudin
Keyword(s):  
Data Analysis ◽  
Power Spectrum ◽  
Low Frequency ◽  
Analytic Description ◽  
Spectral Features ◽  
Spectrum Estimation ◽  
Power Spectrum Estimation ◽  
Murchison Widefield Array ◽  
The Impact ◽  
Expected Signal

ABSTRACT Detecting a signal from the Epoch of Reionization (EoR) requires an exquisite understanding of Galactic and extragalactic foregrounds, low-frequency radio instruments, instrumental calibration, and data analysis pipelines. In this work, we build upon existing work that aims to understand the impact of calibration errors on 21-cm power spectrum (PS) measurements. It is well established that calibration errors have the potential to inhibit EoR detections by introducing additional spectral features that mimic the structure of EoR signals. We present a straightforward way to estimate the impact of a wide variety of modelling residuals in EoR PS estimation. We apply this framework to the specific case of broken dipoles in Murchison Widefield Array (MWA) to understand its effect and estimate its impact on PS estimation. Combining an estimate of the percentage of MWA tiles that have at least one broken dipole (15–40 per cent) with an analytic description of beam errors induced by such dipoles, we compute the residuals of the foregrounds after calibration and source subtraction. We find that that incorrect beam modelling introduces bias in the 2D-PS on the order of $\sim 10^3\, \mathrm{mK}^2 \, h^{-3}\, \mathrm{Mpc}^{3}$. Although this is three orders of magnitude lower than current lowest limits, it is two orders of magnitude higher than the expected signal. Determining the accuracy of both current beam models and direction-dependent calibration pipelines is therefore crucial in our search for an EoR signal.

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