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

Majumdar, Suman; Datta, Kanan K.; Ghara, Raghunath; Mondal, Rajesh; Choudhury, Tirthankar Roy; Bharadwaj, Somnath; Ali, Sk Zeeshan; Datta, Abhirup

doi:10.1007/s12036-016-9402-0

Cited by 9 publications

(7 citation statements)

References 64 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Bharadwaj & Ali 2004;Barkana & Loeb 2005;Mao et al 2012;Majumdar, Bharadwaj & Choudhury 2013;Jensen et al 2013a;Fialkov, Barkana & Cohen 2015;Majumdar et al 2016b) and the "light cone effect" arising due to the finite light travel time (see e.g. Barkana & Loeb 2006;Datta et al 2012Datta et al , 2014Zawada et al 2014;La Plante et al 2014;Majumdar et al 2016a;Mondal, Bharadwaj & Datta 2017) in our simulated signal. These effects will introduce anisotropies in the signal along the line-of-sight of a present day observer and in turn can affect towards the contribution from the various constituents fields on the EoR 21-cm bispectrum.…”

Section: Discussionmentioning

confidence: 67%

“…The spherically-averaged power spectrum achieves a higher signal to noise ratio by averaging the signal over spherical shells in Fourier space, while still preserving many important features of the signal (e.g. Bharadwaj & Ali 2004; Barkana & Loeb 2005;Datta, Choudhury & Bharadwaj 2007;McQuinn et al 2007;Mesinger & Furlanetto 2007;Lidz et al 2008;Choudhury, Haehnelt & Regan 2009;Mao et al 2012;Majumdar, Bharadwaj & Choudhury 2013;Majumdar et al 2016a;Jensen et al 2013a). Thus, in principle it can be used for the EoR parameter estimation with the upcoming SKA1-LOW Greig, Mesinger & Koopmans 2015;Koopmans et al 2015).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

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

Self Cite

128

149

View full text Add to dashboard Cite

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.

show abstract

Section: Discussionmentioning

confidence: 67%

Section: Introductionmentioning

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

Self Cite

128

149

View full text Add to dashboard Cite

show abstract

“…Note that we have ignored the presence of redshift space distortions (RSD) while evaluating the power spectrum for different model parameters, as their impact remains rather small during the epoch of our interest 10 , when ionization fluctu-9 Partnership for Advanced Computing in Europe: http://www. prace-ri.eu/ 10 The effects of RSD can enhance the large-scale power spectrum by a ations dominate the power spectrum of 𝛿𝑇 b (Jensen et al 2013;Majumdar et al 2016;Ghara et al 2015a,b;Ross et al 2020).…”

Section: Modelling the 21-cm Signal Usingmentioning

confidence: 99%

Constraining the intergalactic medium at z ≈ 9.1 using LOFAR Epoch of Reionization observations

Ghara

Giri

Mellema

et al. 2020

Monthly Notices of the Royal Astronomical Society

108

View full text Add to dashboard Cite

We derive constraints on the thermal and ionization states of the intergalactic medium (IGM) at redshift ≈ 9.1 using new upper limits on the 21-cm power spectrum measured by the LO-FAR radio-telescope and a prior on the ionized fraction at that redshift estimated from recent cosmic microwave background (CMB) observations. We have used results from the reionization simulation code GRIZZLY and a Bayesian inference framework to constrain the parameters which describe the physical state of the IGM. We find that, if the gas heating remains negligible, an IGM with ionized fraction 0.13 and a distribution of the ionized regions with a characteristic size 8 h −1 comoving megaparsec (Mpc) and a full width at the half maximum (FWHM) 16 h −1 Mpc is ruled out. For an IGM with a uniform spin temperature T S 3 K, no constraints on the ionized component can be computed. If the large-scale fluctuations of the signal are driven by spin temperature fluctuations, an IGM with a volume fraction 0.34 of heated regions with a temperature larger than CMB, average gas temperature 7-160 K and a distribution of the heated regions with characteristic size 3.5-70 h −1 Mpc and FWHM of 110 h −1 Mpc is ruled out. These constraints are within the 95 per cent credible intervals. With more stringent future upper limits from LOFAR at multiple redshifts, the constraints will become tighter and will exclude an increasingly large region of the parameter space.

show abstract

“…There are, however, some effects that can make the signal anisotropic, such as redshift-space distortions [81,82] and the effect of the lightcone [83,84] (as we only take coevaluated boxes). These effects can be sizable on large scales [85], and potentially affect recovery of parameters from data [86,87]. Nonetheless, the VAO signal is expected to be isotropic, so we leave detailed studies of the effect of LoS anisotropies for future work.…”

Section: During the Epoch Of Heatingmentioning

confidence: 99%

Robust velocity-induced acoustic oscillations at cosmic dawn

Muñoz

2019

Phys. Rev. D

106

View full text Add to dashboard Cite

The redshifted 21-cm line of hydrogen holds great potential for the study of cosmology, as it can probe otherwise unobservable cosmic epochs. In particular, measurements of the 21-cm power spectrum during cosmic dawn-the era when the first stars were formed-will provide us with a wealth of information about the astrophysics of stellar formation, as well as the origin of fluctuations in our Universe. In addition to their usually considered density fluctuations, dark matter and baryons possess large relative velocities with respect to each other, due to the baryon acoustic oscillations (BAOs) suffered by the latter, which suppress the formation of stars during cosmic dawn, leaving an imprint on 21-cm observables during this era. Here we present 21cmvFAST, a version of the publicly available code 21cmFAST modified to account for this effect. Previous work has shown that the inclusion of relative velocities produces an acoustic modulation on the large-scale 21-cm power spectrum during cosmic dawn. By comparing analytic calculations with simulations from 21cmvFAST, here we demonstrate that this modulation takes the form of robust velocity-induced acoustic oscillations (VAOs), during both the Lyman-α coupling era and the subsequent epoch of heating. The unique shape of these VAOs, which is determined by the acoustic physics that generated the relative velocities, can be analytically computed and is easily distinguishable from the usual density-sourced fluctuations. We find that, under a broad range of astrophysical assumptions, the VAOs are detectable at high significance by the upcoming HERA interferometer, which could therefore confirm the presence of acoustic oscillations at cosmic dawn.

show abstract

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

Cited by 9 publications

References 64 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

Constraining the intergalactic medium at z ≈ 9.1 using LOFAR Epoch of Reionization observations

Robust velocity-induced acoustic oscillations at cosmic dawn

Contact Info

Product

Resources

About