Calibration and 21-cm Power Spectrum Estimation in the Presence of Antenna Beam Variations

Abstract

Detecting a signal from the Epoch of Reionisation (EoR) requires an exquisite understanding of galactic and extra-galactic 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%) 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.

14 pages, 8 figures. Accepted for publication in MNRAS December 2019. Erratum submitted on 20 February 2020

References in corpus (12)

• The NumPy array: a structure for efficient numerical computation
• The Epoch of Reionization Window: I. Mathematical Formalism
• Foreground simulations for the LOFAR - Epoch of Reionization Experiment
• A Method for 21cm Power Spectrum Estimation in the Presence of Foregrounds
• Real-Time Calibration of the Murchison Widefield Array
• Fast Holographic Deconvolution: a new technique for precision radio interferometry
• Distributed Radio Interferometric Calibration
• The contribution of the Unresolved Extragalactic Radio Sources to the Brightness Temperature of the sky
• A Fast Method for Power Spectrum and Foreground Analysis for 21 cm Cosmology
• The FHD/$\mathbf{\epsilon }$ppsilon Epoch of Reionization Power Spectrum Pipeline
• An Improved Statistical Point-Source Foreground Model for the Epoch of Reionization
• Data Multiplexing in Radio Interferometric Calibration

Cited by in corpus (7)

• A new MWA limit on the 21 cm Power Spectrum at Redshifts $\sim$ 13 $-$ 17
• First multi-redshift limits on post-Epoch of Reionization (post-EoR) 21 cm signal from z = 1.96 - 3.58 using uGMRT
• Exploring the cosmic dawn and epoch of reionization with 21cm line
• Dual Polarization Measurements of MWA Beampatterns at 137 MHz
• On the use of temporal filtering for mitigating galactic synchrotron calibration bias in 21 cm reionization observations
• The Role of the Instrumental Response in 21 cm EoR Power Spectrum Gridding Analyses
• Epoch of Reionization Power Spectrum Limits from Murchison Widefield Array Data Targeted at EoR1 Field