2018MNRAS.474.4552G -
Mon. Not. R. Astron. Soc., 474, 4552-4563 (2018/March-2)
Deconvolving the wedge: maximum-likelihood power spectra via spherical-wave visibility modelling.
GHOSH A., MERTENS F.G. and KOOPMANS L.V.E.
Abstract (from CDS):
Direct detection of the Epoch of Reionization (EoR) via the red-shifted 21-cm line will have unprecedented implications on the study of structure formation in the infant Universe. To fulfil this promise, current and future 21-cm experiments need to detect this weak EoR signal in the presence of foregrounds that are several orders of magnitude larger. This requires extreme noise control and improved wide-field high dynamic-range imaging techniques. We propose a new imaging method based on a maximum likelihood framework which solves for the interferometric equation directly on the sphere, or equivalently in the uvw-domain. The method uses the one-to-one relation between spherical waves and spherical harmonics (SpH). It consistently handles signals from the entire sky, and does not require a w-term correction. The SpHcoefficients represent the sky-brightness distribution and the visibilities in the uvw-domain, and provide a direct estimate of the spatial power spectrum. Using these spectrally smooth SpH coefficients, bright foregrounds can be removed from the signal, including their side-lobe noise, which is one of the limiting factors in high dynamics-range wide-field imaging. Chromatic effects causing the so-called 'wedge' are effectively eliminated (i.e. deconvolved) in the cylindrical (k⊥, k||) power spectrum, compared to a power spectrum computed directly from the images of the foreground visibilities where the wedge is clearly present. We illustrate our method using simulated Low-Frequency Array observations, finding an excellent reconstruction of the input EoR signal with minimal bias.
Abstract Copyright:
© 2017 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society
Journal keyword(s):
methods: data analysis - techniques: interferometric - diffuse radiation - large-scale structure of Universe - cosmology: observations
Simbad objects:
1
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