Quantifying the non-Gaussianity in the EoR 21-cm signal through bispectrum
File(s)
Published version
Author(s)
Type
Journal Article
Abstract
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 higher order 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 (xHI) field and fluctuations in the matter density field. We find that the non-Gaussian contribution from these two sources varies, 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 evolving x¯HI or redshift), through the trajectories of the signal in a power spectrum and equilateral bispectrum i.e. P(k) − B(k, k, k) space.
Date Issued
2018-05-01
Date Acceptance
2018-02-23
Citation
Monthly Notices of the Royal Astronomical Society, 2018, 476 (3), pp.4007-4024
ISSN
0035-8711
Publisher
Oxford University Press (OUP)
Start Page
4007
End Page
4024
Journal / Book Title
Monthly Notices of the Royal Astronomical Society
Volume
476
Issue
3
Copyright Statement
©2018 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Identifier
http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000430944100077&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=1ba7043ffcc86c417c072aa74d649202
Subjects
Science & Technology
Physical Sciences
Astronomy & Astrophysics
methods: numerical
dark ages, reionization, first stars
21 CM SIGNAL
SPIN-TEMPERATURE-FLUCTUATIONS
REDSHIFT-SPACE DISTORTIONS
SPECTRUM ERROR-COVARIANCE
LIGHT-CONE ANISOTROPY
LY-ALPHA EMITTERS
POWER-SPECTRUM
COSMIC DAWN
INTERGALACTIC MEDIUM
CENTIMETER FLUCTUATIONS
Publication Status
Published
Date Publish Online
2018-02-27