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Published May 21, 2016 | Published + Submitted
Journal Article Open

Scintillation noise power spectrum and its impact on high-redshift 21-cm observations

Abstract

Visibility scintillation resulting from wave propagation through the turbulent ionosphere can be an important source of noise at low radio frequencies (ν ≲ 200 MHz). Many low-frequency experiments are underway to detect the power spectrum of brightness temperature fluctuations of the neutral-hydrogen 21-cm signal from the Epoch of Reionization (EoR: 12 ≳ z ≳ 7, 100 ≲ ν ≲ 175 MHz). In this paper, we derive scintillation noise power spectra in such experiments while taking into account the effects of typical data processing operations such as self-calibration and Fourier synthesis. We find that for minimally redundant arrays such as LOFAR and MWA, scintillation noise is of the same order of magnitude as thermal noise, has a spectral coherence dictated by stretching of the snapshot uv-coverage with frequency, and thus is confined to the well-known wedge-like structure in the cylindrical (two-dimensional) power spectrum space. Compact, fully redundant (d_(core) ≲ r_F ≈ 300 m at 150 MHz) arrays such as HERA and SKA-LOW (core) will be scintillation noise dominated at all baselines, but the spatial and frequency coherence of this noise will allow it to be removed along with spectrally smooth foregrounds.

Additional Information

© 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2016 February 22. Received 2016 February 22; in original form 2015 November 12. First published online February 26, 2016. The authors thank Dr Maaijke Mevius and Professor A.G. de Bruyn for many interesting discussions. The authors also acknowledge the financial support from the European Research Council under ERC-Starting Grant FIRSTLIGHT - 258942.

Attached Files

Published - MNRAS-2016-Vedantham-3099-117.pdf

Submitted - 1512.00159v1.pdf

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