Sensitivity for 21 cm bispectrum from Epoch of Reionization

Abstract

The 21cm line brightness temperature brings rich information about Epoch of Reionizaton (EoR) and high-z universe (Cosmic Dawn and Dark Age). While the power spectrum is a useful tool to investigate the EoR signal statistically, higher-order statistics such as bispectrum are also valuable because the EoR signal is expected to be highly non-Gaussian. In this paper, we develop a formalism to calculate the bispectrum contributed from the thermal noise taking array configularion of telescopes into account, by extending a formalism for the power spectrum. We apply our formalism to the ongoing and future telescopes such as expanded Murchison Widefield Array (MWA), LOw Frequency ARray (LOFAR) , Hydrogen Epoch of Reionization Array (HERA) and Square Kilometre Array (SKA). We find that expanded MWA does not have enough sensitivity to detect the bispectrum signal. On the other hand, LOFAR has better sensitivity and will be able to detect the peaks of the bispectrum as a function of redshift at large scales with comoving wavenumber k 0.03 Mpc −1 . The SKA has enough sensitivity to detect the bispectrum for much smaller scales k 0.3 Mpc −1 and redshift z 20

Gridded and direct Epoch of Reionisation bispectrum estimates using the Murchison Widefield Array

“…The gridded bispectrum noise scales with observation time to the power of 1.5, requiring a 1 000 h observation with the MWA to achieve a cosmological detection. This estimate is in line with predictions from Yoshiura et al (2015). Further advantage may be gained from incoherent addition of isosceles triangle configurations with similar vector lengths, where the bispectrum is expected to vary slowly with changing parameters.…”

The impact of non-Gaussianity on the error covariance for observations of the Epoch of Reionization (EoR) 21-cm power spectrum

“…Only weak upper limits on the EoR 21-cm PS have been estimated till date (McGreer, Mesinger & Fan 2011;Parsons et al 2014;Pober, Greig & Mesinger 2016a). In addition to the PS, various other statistics such as the variance (Patil et al 2014), bispectrum (Yoshiura et al 2015;Shimabukuro et al 2017;Majumdar et al 2018), and the Minkowski Functional (Bag et al 2018;Kapahtia et al 2018) have been proposed to quantify the EoR 21-cm signal .…”

Studying the morphology of H iisodensity surfaces during reionization using Shapefinders and percolation analysis

“…The figure shows that the area under the 'hysteresis' actually increases with decreasing redshift indicating the significant increase of non-Gaussianity in the HI field as the universe evolves through reionization as well as structure formation in time. In recent times, efforts have been made to analyze the amount of non-Gaussianity in the 21-cm fields using higher order correlation functions (Bharadwaj & Pandey 2005;Cooray 2005;Pillepich et al 2007;Mondal et al 2015;Yoshiura et al 2015;Majumdar et al 2018). Complementary to the bispectrum statistics, in this paper, the growth of non-gaussianity with reionization has been demonstrated from the geometrical point of view using the percolation curves.…”