IPMU Colloquium

Speaker: Hyunbae Park (Kavli IPMU)
Title: Variation in the Reionization History Caused by Baryon-dark Matter Streaming Velocity
Date (JST): Fri, Oct 09, 2020, 15:00 - 16:00
Place: Zoom
Related File: 2577.pdf
Abstract: The reionization era is the first billion years in cosmic history when the gas outside galaxies was gradually ionized star-light. Interestingly, recent observations find a variation of 0.1 billion years in when the reionization ended. That difference in time translates to 150 megaparsec in the distance, and it is puzzling to explain how the universe can be inhomogeneous at such a large scale. In this study, we attempt to explain the variation from the relative streaming motion between baryon-dark matter originated from the Baryonic Acoustic Oscillation. The streaming motion fluctuates in space at ~150 megaparsec scales. Thus, the streaming velocity can be high in one place and low in the other. Using a series of numerical simulations, we show that the streaming strongly suppresses the formation of small-scale gas structures between galaxies. Fewer gas structures lead to less recombination when the gas is ionized. Thus, fewer ionizing photons are needed to ionize the gas allowing the reionization proceeds faster in the highly streaming regions. In our model, the variation in the end-of-reionization caused by the streaming effect is as large as the observed value, suggesting that the streaming motion is a promising explanation for the observed variation.
Remarks: IPMU Postdoc Colloquium Series 1
Registration necessary from here: https://ipmu.zoom.us/webinar/register/WN_rXZI0jiVSX6E6GgIo8-u-w