The multi-frequency angular power spectrum of the epoch of reionization 21 cm signal

Abstract

Observations of redshifted 21cm radiation from HI at high redshifts is an important future probe of reionization. We consider the Multi-frequency Angular Power Spectrum (MAPS) to quantify the statistics of the HI signal as a joint function of the angular multipole l and frequency separation Δν. The signal at two different frequencies is expected to get decorrelated as Δνis increased, and quantifying this decorrelation is particularly important in deciding the frequency resolution for future HI observations. This is also expected to play a very crucial role in extracting the signal from foregrounds as the signal is expected to decorrelate much faster than the foregrounds (which are largely continuum sources) with increasing Δν. In this paper we develop formulae relating the MAPS to different components of the three dimensional HI power spectrum taking into account HI peculiar velocities. We show that the flat-sky approximation provides a very good representation over the angular scales of interest, and a final expression which is very simple to calculate and interpret. We present results considering two models for the HI distribution, namely, (i) DM: where the HI traces the dark matter and (ii) PR: where the effects of patchy reionization are incorporated through two parameters. We find that while the DM signal is largely featureless, the PR signal peaks at the angular scales of the individual bubbles, and the signal is considerably enhanced for large bubble size. For most cases of interest at l \sim 100 the signal is uncorrelated beyond Δν\sim 1 MHz or even less, whereas it occurs around \sim 0.1 MHz at l \sim 10^3. The Δνdependence also carries an imprint of the bubble size and the bias, and is expected to be an important probe of the reionization scenario (abridged).

Accepted for publication in MNRAS. Revised to match the accepted version

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Cited by in corpus (9)

• The 21cm angular-power spectrum from the dark ages
• Foregrounds for redshifted 21 cm studies of reionization: GMRT 153 MHz observations
• Estimation of Cosmological Parameters from HI Observations of Post-reionization Epoch
• Detecting ionized bubbles in redshifted 21 cm maps
• Non-linear Redshift-Space Power Spectra
• Simulating the impact of HI fluctuations on matched filter search for ionized bubbles in redshifted 21 cm maps
• The CMBR ISW and HI 21-cm Cross-correlation Angular Power Spectrum
• Gravitational Wave Detection Using Redshifted 21-cm Observations
• Probing Cosmological Reionization through Radio-interferometric Observations of Neutral Hydrogen