Redshift-space distortions in simulations of the 21-cm signal from the cosmic dawn

Ross, Hannah E; Giri, Sambit K.; Mellema, Garrelt; Dixon, Keri L.; Ghara, Raghunath; Iliev, Ilian T.

doi:10.1093/mnras/stab1822

Cited by 25 publications

(10 citation statements)

References 94 publications

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“…Previous studies have shown that with SKA-Low, such an observation time will yield a sufficient signal-to-noise ratio (SNR) to study the properties of cosmic dawn [e.g. 2,62,74,77,82,88]. We furthermore assume a bandwidth of 10 MHz.…”

Section: A Mock Observationsmentioning

confidence: 99%

Imprints of fermionic and bosonic mixed dark matter on the 21-cm signal at cosmic dawn

Giri,

Schneider

2022

Preprint

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The 21-cm signal from the epoch of cosmic dawn prior to reionization consists of a promising observable to gain new insights into the dark matter (DM) sector. In this paper, we investigate its potential to constrain mixed (cold + non-cold) dark matter scenarios that are characterised by the non-cold DM fraction (fnCDM) and particle mass (mnCDM). As non-cold DM species, we investigate both a fermionic (sterile neutrino) and a bosonic (ultra-light axion) particle. We show how these scenarios affect the global signal and the power spectrum using a halo-model implementation of the 21-cm signal at cosmic dawn. Next to this study, we perform an inference-based forecast study based on realistic mock power spectra from the Square Kilometre Array (SKA) telescope. Assuming inefficient, yet non-zero star-formation in minihaloes (i.e. haloes with mass below 10 8 M ), we obtain stringent constraints on both mnCDM and fnCDM that go well beyond current limits. Regarding the special case of fnCDM ∼ 1, for example, we find a constraint of mnCDM > 15 keV (thermal mass) for fermionic DM and mnCDM > 2 × 10 −20 eV for bosonic DM. For the opposite case of dominating cold DM, we find that at most one percent of the total DM abundance can be made of a hot fermionic or bosonic relic. All constraints are provided at the 95 percent confidence level.

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Section: A Mock Observationsmentioning

confidence: 99%

Imprints of fermionic and bosonic mixed dark matter on the 21-cm signal at cosmic dawn

Giri,

Schneider

2022

Preprint

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“…Lastly, we did not include redshift space distortions or the light cone effect, which have both been shown to alter the shape of the 21-cm power spectrum (e.g. Barkana & Loeb 2006;Mao et al 2012;Datta et al 2012;Mondal et al 2018;Ross et al 2021). However, a preliminary check showed no major changes to the evolution of the decomposition when redshift space distortions were included.…”

Section: Generality Of the Decompositionmentioning

confidence: 99%

The large-scale 21-cm power spectrum from reionization

Georgiev,

Mellema,

Giri

et al. 2021

Preprint

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Radio interferometers, such as the Low-Frequency Array (LOFAR) and the future Square Kilometre Array (SKA), are attempting to measure the spherically averaged 21-cm power spectrum from the Epoch of Reionization (EoR). Understanding of the dominant physical processes which influence the power spectrum at each length-scale is therefore crucial for interpreting any future detection. We study a decomposition of the 21-cm power spectrum and quantify the evolution of its constituent terms for a set of numerical and semi-numerical simulations of a volume of (714 Mpc) 3 , focusing on large scales with 𝑘 0.3 Mpc −1 After ∼ 10 per cent of the Universe has been ionized, the 21-cm power spectrum follows the power spectrum of neutral hydrogen fluctuations, which itself beyond a certain scale follows the matter power spectrum. Hence the signal has a two-regime form where the large-scale signal is a biased version of the cosmological density field, and the small-scale power spectrum is determined by the astrophysics of reionization. We construct a bias parameter to investigate which 𝑘-scales of the large-scale 21-cm signal can be utilised as a probe of cosmology. We find that the transition scale between the scale-independent and scale-dependent bias regimes is directly related to the value of the mean free path of ionizing photons (𝜆 MFP ), and is characterised by the empirical formula 𝑘 trans ≈ 2/𝜆 MFP . Furthermore, we show that the numerical implementation of the mean free path effect has a significant impact on the shape of this transition. Most notably, the transition is more gradual if the mean free path effect is implemented as an absorption process rather than as a barrier.

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“…By definition, the power spectrum provides the auto-correlation between the signal at a single Fourier mode and thus cannot capture this non-Gaussianity. The fundamental statistics which can capture this non-Gaussianity are skewness and kurtosis [21,[49][50][51][52][53][54]. However, these statistics can only probe the non-Gaussian features at a single length scale.…”

Section: Introductionmentioning

confidence: 99%

Redshifted 21-cm bispectrum: Impact of the source models on the signal and IGM physics from the Cosmic Dawn

Kamran¹,

Ghara²,

Majumdar³

et al. 2022

Preprint

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The radiations from the first luminous sources drive the fluctuations in the 21-cm signal at Cosmic Dawn (CD) via two dominant astrophysical processes i.e. the Ly𝛼 coupling and X-ray heating, making this signal highly non-Gaussian. The impact of these processes on the 21-cm signal and its non-Gaussianity vary depending on the properties of these first sources of light. In this work, we consider different CD scenarios by varying two major source parameters i.e. the minimum halo mass 𝑀 h, min and X-ray photon production efficiency 𝑓 X in a 1D radiative transfer code . We study the impact of variation in these source parameters on the large scale (𝑘 1 = 0.16 Mpc −1 ) 21-cm bispectrum for all possible unique triangles in the Fourier domain. Our detailed and comparative analysis of the power spectrum and bispectrum shows that the shape, sign and magnitude of the bispectrum combinedly provide the best measure of the signal fluctuations and its non-Gaussianity compared to the power spectrum. We also conclude that it is important to study the sequence of sign changes along with the variations in the shape and magnitude of the bispectrum throughout the CD history to arrive at a robust conclusion about the dominant IGM processes at different cosmic times. We further observe that among all the possible unique 𝑘-triangles, the large-scale non-Gaussianity in signal is best probed by the small 𝑘-triangles in the squeezed limit and by triangles of similar shapes. This opens up the possibility of constraining the source parameters during the CD using the 21-cm bispectrum.

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Redshift-space distortions in simulations of the 21-cm signal from the cosmic dawn

Cited by 25 publications

References 94 publications

Imprints of fermionic and bosonic mixed dark matter on the 21-cm signal at cosmic dawn

Imprints of fermionic and bosonic mixed dark matter on the 21-cm signal at cosmic dawn

The large-scale 21-cm power spectrum from reionization

Redshifted 21-cm bispectrum: Impact of the source models on the signal and IGM physics from the Cosmic Dawn

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