Ghosh, Abhik; Koopmans, Léon V. E.; Chapman, E.; Jelić, Vibor (2015) A Bayesian analysis of redshifted 21cm H I signal and foregrounds: simulations for LOFAR. Monthly notices of the Royal Astronomical Society, 452 (2). pp. 15871600. ISSN 00358711

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Abstract
Observations of the epoch of reionization (EoR) using the 21cm hyperfine emission of neutral hydrogen (H I) promise to open an entirely new window on the formation of the first stars, galaxies and accreting black holes. In order to characterize the weak 21 cm signal, we need to develop imaging techniques that can reconstruct the extended emission very precisely. Here, we present an inversion technique for LOw Frequency ARray (LOFAR) baselines at the North Celestial Pole (NCP), based on a Bayesian formalism with optimal spatial regularization, which is used to reconstruct the diffuse foreground map directly from the simulated visibility data. We notice that the spatial regularization denoises the images to a large extent, allowing one to recover the 21cm power spectrum over a considerable k⊥k∥ space in the range 0.03 Mpc1 < k⊥ < 0.19 Mpc1 and 0.14 Mpc1 < k∥ < 0.35 Mpc1 without subtracting the noise power spectrum. We find that, in combination with using generalized morphological component analysis (GMCA), a nonparametric foreground removal technique, we can mostly recover the spherical average power spectrum within 2σ statistical fluctuations for an input Gaussian random rootmeansquare noise level of 60 mK in the maps after 600 h of integration over a 10MHz bandwidth.
Item Type:  Article 

Uncontrolled Keywords:  methods; data analysis; technique; interferometric; cosmology; general; diffuse radiation; radio continuum; general 
Subjects:  NATURAL SCIENCES > Physics NATURAL SCIENCES > Physics > Astronomy and Astrophysics 
Divisions:  Division of Experimental Physics 
Depositing User:  Vibor Jelić 
Date Deposited:  27 Aug 2015 13:56 
Last Modified:  26 Jan 2016 13:31 
URI:  http://fulir.irb.hr/id/eprint/2103 
DOI:  10.1093/mnras/stv1355 
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