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Redshifted 21-cm bispectrum II: Impact of the spin temperature fluctuations and redshift space distortions on the signal from the Cosmic Dawn
Cosmology and Nongalactic Astrophysics · Submitted 21 Dec 2020
abstract compiled · 2026-09-23 · no language-model review
The authors' main claim This feature can be used in principle to constrain the CD history and/or to identify the specific CD scenarios.
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The abstract, sentence by sentence
We present a study of the 21-cm signal bispectrum (which quantifies the non-Gaussianity in the signal) from the Cosmic Dawn (CD). For our analysis, we have simulated the 21-cm signal using radiative transfer code GRIZZLY, while considering two types of sources (mini-QSOs and HMXBs) for Ly$\alpha$ coupling and the X-ray heating of the IGM. Using this simulated signal, we have, for the first time, estimated the CD 21-cm bispectra for all unique $k$-triangles and for a range of $k$ modes. We observe that the redshift evolution of the bispectra magnitude and sign follow a generic trend for both source models. However, the redshifts at which the bispectra magnitude reach their maximum and minimum values and show their sign reversal depends on the source model. When the Ly$\alpha$ coupling and the X-ray heating of the IGM occur simultaneously, we observe two consecutive sign reversals in the bispectra for small $k$-triangles (irrespective of the source models). One arising at the beginning of the IGM heating and the other at the end of Ly$\alpha$ coupling saturation. This feature can be used in principle to constrain the CD history and/or to identify the specific CD scenarios. We also quantify the impact of the spin temperature ($T_{\rm S}$) fluctuations on the bispectra. We find that $T_{\rm S}$ fluctuations have maximum impact on the bispectra magnitude for small $k$-triangles and at the stage when Ly$\alpha$ coupling reaches saturation. Furthermore, we are also the first to quantify the impact of redshift space distortions (RSD), on the CD bispectra. We find that the impact of RSD on the CD 21-cm bispectra is significant ($> 20\%$) and the level depends on the stages of the CD and the $k$-triangles for which the bispectra are being estimated.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | We present a study of the 21-cm signal bispectrum (which quantifies the non-Gaussianity in the signal) from the Cosmic Dawn (CD). | contribution 0.99 | 0.90 | 0.05 | asserted 0.93 |
| s1 | For our analysis, we have simulated the 21-cm signal using radiative transfer code GRIZZLY, while considering two types of sources (mini-QSOs and HMXBs) for Ly$\alpha$ coupling and the X-ray heating of the IGM. | method 1.00 | 0.94 | 0.02 | asserted 0.98 |
| s2 | Using this simulated signal, we have, for the first time, estimated the CD 21-cm bispectra for all unique $k$-triangles and for a range of $k$ modes. | contribution 0.93 | 0.97 | 0.08 | asserted 1.00 |
| s3 | We observe that the redshift evolution of the bispectra magnitude and sign follow a generic trend for both source models. | result 1.00 | 0.94 | 0.14 | asserted 1.00 |
| s4 | However, the redshifts at which the bispectra magnitude reach their maximum and minimum values and show their sign reversal depends on the source model. | result 1.00 | 0.93 | 0.16 | asserted 1.00 |
| s5 | When the Ly$\alpha$ coupling and the X-ray heating of the IGM occur simultaneously, we observe two consecutive sign reversals in the bispectra for small $k$-triangles (irrespective of the source models). | result 1.00 | 0.96 | 0.23 | asserted 1.00 |
| s6 | One arising at the beginning of the IGM heating and the other at the end of Ly$\alpha$ coupling saturation. | result 0.96 | 0.80 | 0.07 | asserted 0.98 |
| s7 | This feature can be used in principle to constrain the CD history and/or to identify the specific CD scenarios. | interpretation 0.99 | 0.32 | 0.22 | hedged possibility 0.99 |
| s8 | We also quantify the impact of the spin temperature ($T_{\rm S}$) fluctuations on the bispectra. | contribution 0.95 | 0.92 | 0.05 | asserted 0.66 |
| s9 | We find that $T_{\rm S}$ fluctuations have maximum impact on the bispectra magnitude for small $k$-triangles and at the stage when Ly$\alpha$ coupling reaches saturation. | result 1.00 | 0.97 | 0.11 | asserted 1.00 |
| s10 | Furthermore, we are also the first to quantify the impact of redshift space distortions (RSD), on the CD bispectra. | contribution 0.98 | 0.95 | 0.11 | asserted 1.00 |
| s11 | We find that the impact of RSD on the CD 21-cm bispectra is significant ($> 20\%$) and the level depends on the stages of the CD and the $k$-triangles for which the bispectra are being estimated. | result 1.00 | 0.97 | 0.19 | asserted 1.00 |
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The paper
Original abstract
We present a study of the 21-cm signal bispectrum (which quantifies the non-Gaussianity in the signal) from the Cosmic Dawn (CD). For our analysis, we have simulated the 21-cm signal using radiative transfer code GRIZZLY, while considering two types of sources (mini-QSOs and HMXBs) for Ly$\alpha$ coupling and the X-ray heating of the IGM. Using this simulated signal, we have, for the first time, estimated the CD 21-cm bispectra for all unique $k$-triangles and for a range of $k$ modes. We observe that the redshift evolution of the bispectra magnitude and sign follow a generic trend for both source models. However, the redshifts at which the bispectra magnitude reach their maximum and minimum values and show their sign reversal depends on the source model. When the Ly$\alpha$ coupling and the X-ray heating of the IGM occur simultaneously, we observe two consecutive sign reversals in the bispectra for small $k$-triangles (irrespective of the source models). One arising at the beginning of the IGM heating and the other at the end of Ly$\alpha$ coupling saturation. This feature can be used in principle to constrain the CD history and/or to identify the specific CD scenarios. We also quantify the impact of the spin temperature ($T_{\rm S}$) fluctuations on the bispectra. We find that $T_{\rm S}$ fluctuations have maximum impact on the bispectra magnitude for small $k$-triangles and at the stage when Ly$\alpha$ coupling reaches saturation. Furthermore, we are also the first to quantify the impact of redshift space distortions (RSD), on the CD bispectra. We find that the impact of RSD on the CD 21-cm bispectra is significant ($> 20\%$) and the level depends on the stages of the CD and the $k$-triangles for which the bispectra are being estimated.
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References
How the literature uses it
8 arXiv papers cite this in 16 sentences
Papers citing it · 11 sentences without a confident label
Uses its method or tool 1 paper
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Further, we follow the convention of [ref] and [ref] to demonstrate our result in terms of spherically averaged normalized power spectrum and bispectrum that are respectively defined as $Δ^2(k) = [ k^3 P(k)/(2π^2)]$ and $Δ^3(k_1, n, cosθ) = [ k_1^3 k_2^3 B(k_1, k_2, k_3)/(2π^2)^2]$.
Redshifted 21-cm bispectrum: Impact of the source models on the signal and the IGM physics from the Cosmic Dawn · Results · 0.97
Uses its data or values 1 paper
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For this paper, the simulations considered use the gridded dark-matter density fields and the corresponding halo lists within comoving cubes of side 500 $ℎ^-1$ Mpc, produced from the PRACE4LOFAR[Partnership for Advanced Computing in Europe: <http://www.prace-ri.eu/>] N-body simulations (for the details of the simulation, see e.g, [ref] ).
Inferring IGM parameters from the redshifted 21-cm Power Spectrum using Artificial Neural Networks · Modeling the 21-cm signal with grizzly · 0.80
Cites it as support 1 paper
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However, the cumulative effect of radiation source clustering, non-uniform heating, and ionization of the IGM gas by those sources introduce a high level of non-Gaussianity in the CD-EoR 21-cm maps [ref] .
Redshifted 21-cm bispectrum: Impact of the source models on the signal and the IGM physics from the Cosmic Dawn · Introduction · 0.97
Cites it as background 2 papers
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Recent work has investigated the post-reionisation redshift space intensity mapping bispectrum analytically (see e.g. [ref] ), as well as higher-redshift studies with simulated signals [ref] .
The HI intensity mapping bispectrum including observational effects · Introduction · 0.97
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Measurements of the bispectrum of the 21-cm radiation from the cosmic dawn [ref] , the epoch of reionization (e.g. [ref] ) and the post-reionization era (e.g. [ref] ) are expected to yield a wealth of information regarding the evolutionary history of the universe.
A fast estimator for quantifying the shape dependence of the 3D bispectrum · Introduction · 0.84
What it cites · 4 sentences without a confident label
Compares with 1 paper
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[ref] independently produced similar results.
The 21cm bispectrum during reionization: a tracer of the ionization topology · Introduction · 0.94
Cites as background 1 paper
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In the earlier studies [ref] , this phenomenon has been associated with the nature of the non-Gaussianity in the 21-cm signal.
The 21cm bispectrum during reionization: a tracer of the ionization topology · Evolution of the bispectrum sign · 0.82
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