21 cm line bispectrum as a method to probe cosmic dawn and epoch of reionization

Shimabukuro, Hayato; Yoshiura, Shintaro; Takahashi, Keitaro; Yokoyama, Shuichiro; Ichiki, Kiyotomo

doi:10.1093/mnras/stw482

Cited by 65 publications

(55 citation statements)

References 47 publications

(30 reference statements)

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“…The crossover occurs when the linear bias of the neutral hydrogen with respect to the underlying density field is b 1 = −1. At this time, the fluctuations in the hydrogen density are perfectly anti-correlated with the density fluctuations and the 21-cm power spectrum (to linear order) vanishes11 . In all of our models, this epoch of the minimum 21-cm power occurs at x m ≈ 0.13.…”

mentioning

confidence: 87%

“…When applied to the 21-cm signal, eq. (2.9) has the key virtue that it contains more information than the power spectrum, but is simpler to estimate compared to the conventional bispectrum estimators [11,14,15].…”

Section: Position-dependent Power Spectrum As a Probe Of The Squeezedmentioning

confidence: 99%

“…Since the 21-cm signal from reionization is highly non-Gaussian [e.g. 10,11], the power spectrum will not provide a complete statistical description of this process.…”

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confidence: 99%

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Position-dependent power spectra of the 21-cm signal from the epoch of reionization

Giri

D’Aloisio

Mellema

et al. 2019

J. Cosmol. Astropart. Phys.

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The 21-cm signal from the epoch of reionization is non-Gaussian. Current radio telescopes are focused on detecting the 21-cm power spectrum, but in the future the Square Kilometre Array is anticipated to provide a first measurement of the bispectrum. Previous studies have shown that the position-dependent power spectrum is a simple and efficient way to probe the squeezed-limit bispectrum. In this approach, the survey is divided into subvolumes and the correlation between the local power spectrum and the corresponding mean density of the subvolume is computed. This correlation is equivalent to an integral of the bispectrum in the squeezed limit, but is much simpler to implement than the usual bispectrum estimators. It also has a clear physical interpretation: it describes how the smallscale power spectrum of tracers such as galaxies and the 21-cm signal respond to a large-scale environment. Reionization naturally couples large and small scales as ionizing radiation produced by galactic sources can travel up to tens of Megaparsecs through the intergalactic medium during this process. Here we apply the position-dependent power spectrum approach to fluctuations in the 21-cm background from reionization. We show that this statistic has a distinctive evolution in time that can be understood with a simple analytic model. We also show that the statistic can easily distinguish between simple "inside-out" and "outside-in" models of reionization. The position-dependent power spectrum is thus a promising method to validate the reionization signal and to extract higher-order information on this process.

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confidence: 87%

Section: Position-dependent Power Spectrum As a Probe Of The Squeezedmentioning

confidence: 99%

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Position-dependent power spectra of the 21-cm signal from the epoch of reionization

Giri

D’Aloisio

Mellema

et al. 2019

J. Cosmol. Astropart. Phys.

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“…There have been several works modelling the 21-cm bispectrum during various stages of the cosmic evolution covering the dark ages (Pillepich et al 2007), cosmic dawn (Shimabukuro et al 2016), and epoch of reionization (Bharadwaj & Pandey 2005;Chongchitnan 2013;Yoshiura et al 2015;Shimabukuro et al 2017;Majumdar et al 2018;Hoffmann et al 2018). In this paper we focus on the post-reionization 21-cm signal which is expected to be highly non-Gaussian due to the non-linear gravitational instability.…”

Section: Introductionmentioning

confidence: 99%

Modelling the post-reionization neutral hydrogen (H i) 21-cm bispectrum

Sarkar

Majumdar

Bharadwaj

2019

Monthly Notices of the Royal Astronomical Society

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Measurements of the post-reionization 21-cm bispectrum B HI (k 1 , k 2 , k 3 ) using various upcoming intensity mapping experiments hold the potential for determining the cosmological parameters at a high level of precision. In this paper we have estimated the 21-cm bispectrum in the z range 1 z 6 using semi-numerical simulations of the neutral hydrogen (HI) distribution. We determine the k and z range where the 21-cm bispectrum can be adequately modelled using the predictions of second order perturbation theory, and we use this to predict the redshift evolution of the linear and quadratic HI bias parameters b 1 and b 2 respectively. The b 1 values are found to decreases nearly linearly with decreasing z, and are in good agreement with earlier predictions obtained by modelling the 21-cm power spectrum P HI (k). The b 2 values fall sharply with decreasing z, becomes zero at z ∼ 3 and attains a nearly constant value b 2 ≈ −0.36 at z < 2. We provide polynomial fitting formulas for b 1 and b 2 as functions of z. The modelling presented here is expected to be useful in future efforts to determine cosmological parameters and constrain primordial non-Gaussianity using the 21-cm bispectrum.

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“…Thus it is useful to compute higher order statistics and one-point statistics such as the bispectrum, the variance and the skewness to estimate non-gaussian features in the 21cm fluctuations (e.g. Barkana & Loeb 2008;Harker et al 2009;Baek et al 2010;Patil et al 2014;Shimabukuro et al 2015;Shimabukuro et al 2016a).…”

Section: Introduction Of 21cm Power Spectrummentioning

confidence: 99%

Analysing the 21 cm signal from the epoch of reionization with artificial neural networks

Shimabukuro¹,

Semelin²

2017

Monthly Notices of the Royal Astronomical Society

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The 21 cm signal from the Epoch of Reionization should be observed within the next decade. While a simple statistical detection is expected with SKA pathfinders, the SKA will hopefully produce a full 3D mapping of the signal. To extract from the observed data constraints on the parameters describing the underlying astrophysical processes, inversion methods must be developed. For example, the Markov Chain Monte Carlo method has been successfully applied. Here we test another possible inversion method: artificial neural networks (ANN). We produce a training set which consists of 70 individual sample. Each sample is made of the 21 cm power spectrum at different redshifts produced with the 21cmFast code plus the value of three parameters used in the semi-numerical simulations that describe astrophysical processes. Using this set we train the network to minimize the error between the parameter values it produces as an output and the true values. We explore the impact of the architecture of the network on the quality of the training. Then we test the trained network on the new set of 54 test samples with different values of the parameters. We find that the quality of the parameter reconstruction depends on the sensitivity of the power spectrum to the different parameters at a given redshift, that including thermal noise and sample variance decreases the quality of the reconstruction and that using the power spectrum at several redshifts as an input to the ANN improves the quality of the reconstruction. We conclude that ANNs are a viable inversion method whose main strength is that they require a sparse exploration of the parameter space and thus should be usable with full numerical simulations.

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21 cm line bispectrum as a method to probe cosmic dawn and epoch of reionization

Cited by 65 publications

References 47 publications

Position-dependent power spectra of the 21-cm signal from the epoch of reionization

Position-dependent power spectra of the 21-cm signal from the epoch of reionization

Modelling the post-reionization neutral hydrogen (H i) 21-cm bispectrum

Analysing the 21 cm signal from the epoch of reionization with artificial neural networks

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