Effects of the sources of reionization on 21-cm redshift-space distortions

Majumdar, Suman; Jensen, Hannes; Mellema, Garrelt; Chapman, Emma; Abdalla, F. B.; Lee, Kai-Yan; Iliev, Ilian T.; Dixon, Keri L.; Datta, Kanan K.; Ciardi, B.; Fernandez, Elizabeth R.; Jelić, Vibor; Koopmans, L. V. E.; Zaroubi, Saleem

doi:10.1093/mnras/stv2812

Cited by 34 publications

(54 citation statements)

References 84 publications

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“…Note thatMajumdar et al (2016b) has demonstrated the evolution of the EoR 21-cm signal using a similar phase space of monopole and quadrupole moments of the redshift space 21-cm power spectrum.MNRAS 000, 000-000(0000)…”

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confidence: 99%

Quantifying the non-Gaussianity in the EoR 21-cm signal through bispectrum

Majumdar

Pritchard

Mondal

et al. 2018

Monthly Notices of the Royal Astronomical Society

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The epoch of reionization (EoR) 21-cm signal is expected to be highly non-Gaussian in nature and this non-Gaussianity is also expected to evolve with the progressing state of reionization. Therefore the signal will be correlated between different Fourier modes (k). The power spectrum will not be able capture this correlation in the signal. We use a higherorder estimator -the bispectrum -to quantify this evolving non-Gaussianity. We study the bispectrum using an ensemble of simulated 21-cm signal and with a large variety of k triangles. We observe two competing sources driving the non-Gaussianity in the signal: fluctuations in the neutral fraction (x H ) field and fluctuations in the matter density field. We find that the non-Gaussian contribution from these two sources vary, depending on the stage of reionization and on which k modes are being studied. We show that the sign of the bispectrum works as a unique marker to identify which among these two components is driving the non-Gaussianity. We propose that the sign change in the bispectrum, when plotted as a function of triangle configuration cos θ and at a certain stage of the EoR can be used as a confirmative test for the detection of the 21-cm signal. We also propose a new consolidated way to visualize the signal evolution (with evolvingx H or redshift), through the trajectories of the signal in a power spectrum and equilateral bispectrum i.e. P(k) − B(k, k, k) space.

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confidence: 99%

Quantifying the non-Gaussianity in the EoR 21-cm signal through bispectrum

Majumdar

Pritchard

Mondal

et al. 2018

Monthly Notices of the Royal Astronomical Society

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128

149

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“…If the distribution and the properties of the reionization sources change, the topology of the ionization field will also change and one would expect then the phase difference between the matter and the H i field to also change, which it turn should have a signature in the quadrupole moment. To test whether this idea can be used to distinguish between different reionization sources using the nature and amplitude of P s 2 , Majumdar et al (2016) simulated a collection of reionization scenarios considering various degrees of contribution from different kinds of reionization sources. The reionization scenarios they considered include ionizing photon contribution from the usual UV photon sources hosted by the halos with mass 10 9 M , a uniform ionizing background generated by hard X-ray sources, a local uniform ionizing background generated by soft X-ray sources (limited by the mean free path of soft X-ray photons), various combinations of all of these three contributions, reionization driven by quasar like very strong sources located around the most massive halos etc.…”

Section: During the Eormentioning

confidence: 99%

Line-of-Sight Anisotropies in the Cosmic Dawn and Epoch of Reionization 21-cm Power Spectrum

et al. 2016

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Abstract. The line-of-sight direction in the redshifted 21-cm signal coming from the cosmic dawn and the epoch of reionization is quite unique in many ways compared to any other cosmological signal. Different unique effects, such as the evolution history of the signal, non-linear peculiar velocities of the matter etc. will imprint their signature along the line-of-sight axis of the observed signal. One of the major goals of the future SKA-LOW radio interferometer is to observe the cosmic dawn and the epoch of reionization through this 21-cm signal. It is thus important to understand how these various effects affect the signal for its actual detection and proper interpretation. For more than one and half decades, various groups in India have been actively trying to understand and quantify the different line-of-sight effects that are present in this signal through analytical models and simulations. In many ways the importance of this sub-field under 21-cm cosmology have been identified, highlighted and pushed forward by the Indian community. In this article, we briefly describe their contribution and implication of these effects in the context of the future surveys of the cosmic dawn and the epoch of reionization that will be conducted by the SKA-LOW.

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“…This effect is called the redshift-space distortion (RSD) (e.g. Jensen et al 2013;Majumdar et al 2015).…”

Section: Introductionmentioning

confidence: 99%

“…Other work has focused specifically on using the anisotropy generated in the 21-cm signal by the RSDs to separate astrophysical and cosmological affects (e.g. Shaw & Lewis 2008;Shapiro et al 2013;Majumdar et al 2015).…”

Section: Introductionmentioning

confidence: 99%

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

Ross

Giri

Mellema

et al. 2021

Monthly Notices of the Royal Astronomical Society

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The 21-cm signal from the Cosmic Dawn (CD) is likely to contain large fluctuations, with the most extreme astrophysical models on the verge of being ruled out by observations from radio interferometers. It is therefore vital that we understand not only the astrophysical processes governing this signal, but also other inherent processes impacting the signal itself, and in particular line-of-sight effects. Using our suite of fully numerical radiative transfer simulations, we investigate the impact on the redshifted 21-cm from the CD from one of these processes, namely the redshift-space distortions (RSDs). When RSDs are added, the resulting boost to the power spectra makes the signal more or equally detectable for our models for all redshifts, further strengthening hopes that a power spectra measurement of the CD will be possible. RSDs lead to anisotropy in the signal at the beginning and end of the CD, but not while X-ray heating is underway. The inclusion of RSDs, however, decreases detectability of the non-Gaussianity of fluctuations from inhomogeneous X-ray heating as measured by the skewness and kurtosis. On the other hand, mock observations created from all our simulations that include telescope noise corresponding to 1000 hours of observation with the Square Kilometre Array telescope show that we may be able image the CD for all heating models considered and suggest RSDs dramatically boost fluctuations coming from the inhomogeneous Ly-α background.

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Effects of the sources of reionization on 21-cm redshift-space distortions

Cited by 34 publications

References 84 publications

Quantifying the non-Gaussianity in the EoR 21-cm signal through bispectrum

Quantifying the non-Gaussianity in the EoR 21-cm signal through bispectrum

Line-of-Sight Anisotropies in the Cosmic Dawn and Epoch of Reionization 21-cm Power Spectrum

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

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