Naslov
The scale of the problem: recovering images of reionization with Generalized Morphological Component Analysis

Autori
Chapman, Emma ; Abdalla, Filipe B. ; Bobin, J. ; Starck, J.-L. ; Harker, Geraint ; Jelić, Vibor ; Labropoulos, Panagiotis ; Zaroubi, Saleem ; Brentjens, Michiel A. ; de Bruyn, A. G. ; Koopmans, L. V. E.

Izvornik
Monthly notices of the Royal Astronomical Society (0035-8711) 429 (2013), 1; 165-176

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
methods: statistical; cosmology: theory; dark ages; reionization; first stars; diffuse radiation

Sažetak
The accurate and precise removal of 21-cm foregrounds from Epoch of Reionization (EoR) redshifted 21-cm emission data is essential if we are to gain insight into an unexplored cosmological era. We apply a non-parametric technique, Generalized Morphological Component Analysis (gmca), to simulated Low Frequency Array (LOFAR)-EoR data and show that it has the ability to clean the foregrounds with high accuracy. We recover the 21-cm 1D, 2D and 3D power spectra with high accuracy across an impressive range of frequencies and scales. We show that gmca preserves the 21-cm phase information, especially when the smallest spatial scale data is discarded. While it has been shown that LOFAR-EoR image recovery is theoretically possible using image smoothing, we add that wavelet decomposition is an efficient way of recovering 21-cm signal maps to the same or greater order of accuracy with more flexibility. By comparing the gmca output residual maps (equal to the noise, 21-cm signal and any foreground fitting errors) with the 21-cm maps at one frequency and discarding the smaller wavelet scale information, we find a correlation coefficient of 0.689, compared to 0.588 for the equivalently smoothed image. Considering only the pixels in a central patch covering 50 per cent of the total map area, these coefficients improve to 0.905 and 0.605, respectively, and we conclude that wavelet decomposition is a significantly more powerful method to denoise reconstructed 21-cm maps than smoothing.

Izvorni jezik
Engleski

Znanstvena područja
Fizika

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