De-contamination of cosmological 21-cm maps

Abstract

We present a method for extracting the expected cosmological 21-cm signal from the epoch of reionization, taking into account contaminating radiations and random instrumental noise. The method is based on the maximum a-posteriori probability (MAP) formalism and employs the coherence of the contaminating radiation along the line-of-sight and the three-dimensional correlations of the cosmological signal. We test the method using a detailed and comprehensive modeling of the cosmological 21-cm signal and the contaminating radiation. The signal is obtained using a high resolution N-body simulation where the gas is assumed to trace the dark matter and is reionized by stellar radiation computed from semi-analytic galaxy formation recipes. We model contaminations to the cosmological signal from synchrotron and free-free galactic foregrounds and extragalactic sources including active galactic nuclei, radio haloes and relics, synchrotron and free-free emission from star forming galaxies, and free-free emission from dark matter haloes and the intergalactic medium. We provide tests of the reconstruction method for several rms values of instrumental noise from ${\sigma }_N=1$ to 250 mK. For low instrumental noise, the recovered signal, along individual lines-of-sight, fits the true cosmological signal with a mean rms difference of $d_{rms}\approx 1.7\pm 0.6$ for ${\sigma }_N=1$ mK, and $d_{rms}\approx 4.2\pm 0.4$ for ${\sigma }_N=5$ mK. The one-dimensional power spectrum is nicely reconstructed for all values of ${\sigma }_N$ considered here, while the reconstruction of the two-dimensional power spectrum and the Minkowski functionals is good only for noise levels of the order of few mK.

19 pages, 17 figures, accepted for publication in MNRAS

References in corpus (3)

• Foreground simulations for the LOFAR - Epoch of Reionization Experiment
• The X-ray luminosity function and number counts of spiral galaxies
• Heating of the Intergalactic Medium by Primordial Miniquasars

Cited by in corpus (5)

• Foreground simulations for the LOFAR - Epoch of Reionization Experiment
• An Improved Method for 21cm Foreground Removal
• Non-parametric foreground subtraction for 21cm epoch of reionization experiments
• Detection and extraction of signals from the epoch of reionization using higher order one-point statistics
• The LOFAR EoR Data Model: (I) Effects of Noise and Instrumental Corruptions on the 21-cm Reionization Signal-Extraction Strategy