Calibration requirements for epoch of reionization 21-cm signal observations – I. Effect of time-correlated gains

Kumar, Jais; Dutta, Prasun; Roy, Nirupam

doi:10.1093/mnras/staa1371

Cited by 17 publications

(15 citation statements)

References 94 publications

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“…Note that, there are several different ways which may contaminate the foreground free cosmological window above the 'wedge', like residual calibration errors, po-larization leakage, ionospheric effects, the variation of beam, etc and affect the estimation of the Hi 21 cm power spectrum (Gehlot et al 2018;Joseph et al 2020;Kumar et al 2020). Although the estimated power spectrum for different redshift bins are close to the thermal noise, the resultant power spectrum may still be affected by any plausible residual systematics.…”

Section: Resultsmentioning

confidence: 99%

First multi-redshift limits on post-Epoch of Reionization (post-EoR) 21 cm signal from z = 1.96 - 3.58 using uGMRT

Chakraborty,

Datta,

Roy

et al. 2020

Preprint

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Measurement of fluctuations in diffuse Hi 21 cm background radiation from the post-reionization epoch (z ≤ 6) is a promising avenue to probe the large scale structure of the Universe and understand the evolution of galaxies. We observe the European Large-Area ISO Survey-North 1 (ELAIS-N1) field at 300-500 MHz using the upgraded Giant Meterwave Radio Telescope (uGMRT) and employ the 'foreground avoidance' technique to estimate the Hi 21 cm power spectrum in the redshift range z = 1.96 − 3.58. Given the possible systematics that may remain in the data, we find the most stringent upper limits on the spherically averaged 21 cm power spectra at k ∼ 1.0 Mpc −1 are (58.87 mK) 2 , (61.49 mK) 2 , (60.89 mK) 2 , (105.85 mK) 2 at z = 1.96, 2.19, 2.62 and 3.58, respectively. We use this to constrain the product of neutral Hi mass density (Ω HI ) and Hi bias (b HI ) to the underlying dark matter density field, [Ω HI b HI ], as 0.09,0.11,0.12,0.24 at z = 1. 96, 2.19, 2.62, 3.58, respectively. To the best of our knowledge these are the first limits on the Hi 21 cm power spectra at the redshift range z = 1.96 − 3.58 and would play a significant role to constrain the models of galaxy formation and evolution.

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Section: Resultsmentioning

confidence: 99%

First multi-redshift limits on post-Epoch of Reionization (post-EoR) 21 cm signal from z = 1.96 - 3.58 using uGMRT

Chakraborty,

Datta,

Roy

et al. 2020

Preprint

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“…It is to note that this does not suppress the foreground below the 21-cm power spectrum. Kumar et al (2020) demonstrated that the residual grain errors in 21-cm observations in presence of strong foreground is a major challenge for reionization and post reionization power spectrum measurements. The residual gain errors through the strong foreground signal introduce a bias in the 21-cm power spectrum estimates and enhance its variance.…”

Section: Discussionmentioning

confidence: 99%

“…To observe the redshifted 21-cm signal one need to model and subtract the diffused synchrotron foreground signal. Given that the amplitude of the foreground is much higher than the redshifted 21-cm signal, such observations require high dynamic range calibration of the observed visibilities (Datta et al, 2010;Kumar et al, 2020). The lensed 21-cm angular power spectrum estimator reduces the effective amplitude of this foreground and hence improve the calibration requirements.…”

Section: Effect Of Foregroundmentioning

confidence: 99%

Combined lensed estimator to probe the post reionization H I power spectrum

Arora,

Dutta

2021

Preprint

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In the post-reionization era, the baryons assembled into the protogalaxies and eventually the present population of the galaxies evolved through merger and evolution. In this work, we discuss a possible probe of the statistical distribution and evolution of the H I density in the post reionization era. We introduce an estimator of the H I power spectrum from the post reionization universe by observing it through the strong gravitational lenses by the nearby galaxy cluster. We also analytically calculate the uncertainties associated with the estimates of the post-EoR power spectrum for the discussed estimator. We access the efficacy of this estimator in the context of 19 galaxy clusters for which the lensing potential has been estimated earlier by various authors. We find that by combining the lensed power spectrum through eight of these cluster lenses, it is possible to estimate the post-reionization H I power spectrum at five-sigma significance for angular multipoles < 4000 for a uGMRT observation of 16 MHz bandwidth from redshifts of 1.25, 1.5 with a total of 400 hours of observation. With the same setup, for a redshift of 3.0, we need 200 hours of total observation time. The estimator also suppresses the diffused galactic foreground, though, the latter is still a dominant contributor to the overall signal and hence need to be estimated and mitigated. We discuss the merits and demerits of the estimator.

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“…A striking advantage of this approach is that the strong lensing by a lens at a redshift of z l enhances the signal from the redshifted 21-cm emission at a redshift of zs > z l , however, it does not enhance the diffused emission from the Galaxy, which acts as a foreground to the 21-cm signal. The major challenge with the foreground signals like DGSE is that they are inherently several orders of magnitude larger (Di Matteo et al, 2002;Oh & Mack, 2003;Jelić et al, 2008;Ali et al, 2008;Ghosh et al, 2011;Paciga et al, 2013) than the redshifted 21-cm signal and hence effects like residual foregrounds after the subtraction, residual gain errors add to bias in the estimators of the 21-cm power spectra (Datta et al, 2010;Kumar et al, 2020). We observe that for the best cases discussed in this work, that is for the two double halo lens models at a redshift of 0.3, the enhanced visibility correlation signal is still at only a few percent of the expected galactic foreground.…”

Section: Discussionmentioning

confidence: 99%

Using strong gravitational lensing to probe the post reionization \HI power spectrum

Arora,

Dutta

2020

Preprint

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Probing statistical distribution of the neutral hydrogen (H I ) using the redshifted 21-cm hyperfine-transition spectral line holds the key to understand the formation and evolution of the matter density in the universe. The two point statistics of the H I distribution can be estimated by measuring the power spectrum of the redshifted 21-cm signal using visibility correlation. A major challenge in this regard is that the expected signal is weak compared to the foreground contribution from the Galactic synchrotron emission and extragalactic point sources in the observing frequencies. In this work, we investigate the possibility of detecting the power spectrum of the redshifted 21-cm signal by using strong gravitational lensing of the galaxy clusters. This method has the advantage that it only enhances the H I signal and not the diffuse galactic foreground. Based on four simple models of the cluster potentials we show that the strong lenses at relatively lower redshifts with more than one dark matter halo significantly enhances the 21-cm signal from the post reionization era. We discuss the merits and demerits of the method and the future studies required for further investigations.

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Calibration requirements for epoch of reionization 21-cm signal observations – I. Effect of time-correlated gains

Cited by 17 publications

References 94 publications

First multi-redshift limits on post-Epoch of Reionization (post-EoR) 21 cm signal from z = 1.96 - 3.58 using uGMRT

First multi-redshift limits on post-Epoch of Reionization (post-EoR) 21 cm signal from z = 1.96 - 3.58 using uGMRT

Combined lensed estimator to probe the post reionization H I power spectrum

Using strong gravitational lensing to probe the post reionization \HI power spectrum

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