우주 마이크로파 배경복사 편광지도의 통계분석을 통한 우주 재이온화 과정 유추

Abstract

Cosmic reionization is a phenomenon in which hydrogen atoms existing in the intergalactic medium receive energy greater than the ionization energy by an astrophysical light source and are divided into free electrons and nucleus. Photons emitted from the Cosmic Microwave Background are scattered by free electrons, leaving traces in temperature and polarization anisotropy. Currently, as the technology for observing CMB polarization and temperature anisotropy is advancing day by day, it has reached a level that can place many constraints on the history of cosmic reionization. As CMB observations in the near future aim for observations limited by maximum sensitivity and cosmic variance, we predict the potential of future CMB observations to limit reionization history in this study. In this study, We perform Markov-chain Monte-Carlo analysis based on various sampling methods with different schemes and E-mode polarization data obtained by LiteBIRD(Lite satellite for the studies of B-mode Inflation from cosmic background Radiation Detection) that CV-restricted observation instrument to be used in the late 2020s, observe the actual sky that theory based on Ahn & Shapiro(2021). In this study, We focused on the estimation of the partial optical depth of CMB photons τ_(z>15), which can know the reionization rate at the early stage of cosmic reionization. We found τ_(z>15) ~ 0.008 partial optical depth that lower than other recent research result limit partial optical depth that τ_(z>15) ~ 0.02, can reached reionization model that mainly influenced by minihalo in early stage of cosmic reionization, and this model can be distinguish by CV-limited CMB polarization observation from τ_(z>15) ~≤ 5×10^(-4) reionization model. However, there are still difficulties in estimating τ_(z>15) value. Therefore, We investigate that resampling the E-mode polarization data with a limited spherical-harmonics modes can resolve this shortcoming.