Sensitivity for 21 cm bispectrum from Epoch of Reionization

Abstract

The 21cm line brightness temperature brings rich information about Epoch of\nReionizaton (EoR) and high-$z$ universe (Cosmic Dawn and Dark Age). While the\npower spectrum is a useful tool to investigate the EoR signal statistically,\nhigher-order statistics such as bispectrum are also valuable because the EoR\nsignal is expected to be highly non-Gaussian. In this paper, we develop a\nformalism to calculate the bispectrum contributed from the thermal noise taking\narray configularion of telescopes into account, by extending a formalism for\nthe power spectrum \\cite{2006ApJ...653..815M}. We apply our formalism to the\nongoing and future telescopes such as expanded Murchison Widefield Array (MWA),\nLOw Frequency ARray (LOFAR) and Square Kilometre Array (SKA). We find that\nexpanded MWA does not have enough sensitivity to detect the bispectrum signal.\nOn the other hand, LOFAR has better sensitivity and will be able to detect the\npeaks of the bispectrum as a function of redshift at large scales with comoving\nwavenumber $k \\lesssim 0.03 {\\rm Mpc}^{-1}$. The SKA has enough sensitivity to\ndetect the bispectrum for much smaller scales $k \\lesssim 0.3 {\\rm Mpc}^{-1}$\nand redshift $z \\lesssim 20$\n