Detectability of the 21-cm signal during the epoch of reionization with 21-cm Lyman α emitter cross-correlation – I

Abstract

Detection of the redshifted 21cm-line signal from neutral hydrogen in the\nintergalactic medium (IGM) during the Epoch of Reionization (EoR) is\ncomplicated by intense foregrounds such as galactic synchrotron and\nextragalactic radio galaxies. The 21cm-Lyman-$\\alpha$ emitter(LAE)\ncross-correlation is one of the tools available to reduce the foreground\neffects because the foreground emission from such radio sources is\nstatistically independent of LAE distribution. LAE surveys during the EoR at\nredshifts $z=6.6$ and $7.3$ are ongoing by the Subaru Hyper Suprime-Cam (HSC).\nAdditionally, Prime Focus Spectrograph (PFS) will provide precise redshift\ninformation of the LAEs discovered by the HSC survey. In this paper, we\ninvestigate the detectability of the 21cm signal with the 21cm-LAE\ncross-correlation by using our improved reionization simulations. We also focus\non the error budget and evaluate it quantitatively in order to consider a\nstrategy to improve the signal-to-noise ratio. In addition, we explore an\nexpansion of the LAE survey to suggest optimal survey parameters and show a\npotential to measure a characteristic size of ionized bubbles via the turnover\nscale of the cross-power spectrum. As a result, we find that the Murchison\nWidefield Array (MWA) has ability to detect the cross-power spectrum signal on\nlarge scales by combining LAE Deep field survey of HSC. We also show that the\nsensitivity is improved dramatically at small scales by adding redshift\ninformation from the PFS measurements. The Square Kilometre Array (SKA) has a\npotential to measure the turnover scale with an accuracy of\n$6\\times10^{-3}~{\\rm Mpc^{-1}}$.\n