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Wide-field LOFAR-LBA power-spectra analyses: Impact of calibration, polarization leakage and ionosphere

Published online by Cambridge University Press:  08 May 2018

Bharat K. Gehlot  and
Léon V. E. Koopmans
Bharat K. Gehlot*
Affiliation:
Kapteyn Astronomical Institute, University of Groningen, PO Box 800, 9700AV Groningen, the Netherlands
Léon V. E. Koopmans
Affiliation:
Kapteyn Astronomical Institute, University of Groningen, PO Box 800, 9700AV Groningen, the Netherlands
*
*email: gehlot@astro.rug.nl
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Abstract

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Contamination due to foregrounds, calibration errors and ionospheric effects pose major challenges in detection of the cosmic 21 cm signal in various Epoch of Reionization (EoR) experiments. We present the results of a study of a field centered on 3C196 using LOFAR Low Band observations, where we quantify various wide field and calibration effects such as gain errors, polarized foregrounds, and ionospheric effects. We observe a ‘pitchfork’ structure in the power spectrum of the polarized intensity in delay-baseline space, which leaks into the modes beyond the instrumental horizon. We show that this structure arises due to strong instrumental polarization leakage (~30%) towards Cas A which is far away from primary field of view. We measure a small ionospheric diffractive scale towards CasA resembling pure Kolmogorov turbulence. Our work provides insights in understanding the nature of aforementioned effects and mitigating them in future Cosmic Dawn observations.

Keywords

cosmology: observationstechniques: interferometricpolarizationtechniques: polarimetricatmospheric effectsmethods: statistical
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 12 , Symposium S333: Peering towards Cosmic Dawn , October 2017 , pp. 106 - 109
Copyright
Copyright © International Astronomical Union 2018 

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