Models of polarized Lyman-alpha emission from cosmic ionization fronts and extraction of front parameters from 21cmFAST tool
Loading...
Date
2022-05
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
The Ohio State University
Abstract
The epoch of reionization is one main history of the universe, and it gives both
cosmologists and astrophysicists insights into energy radiation, cosmic microwave
background (CMB), galaxy formation, etc. Intensity mapping (IM) is one of the
novel methods in probing the reionization, and Lyman-α forest is one of its main
focuses. Thus, I want to study the epoch of reionization by looking at the Lyman-α
emission from that period. In this paper, I present the formalism of simulating
Lyman-α emission and polarization from a signal plane-parallel ionization front at
redshift z = 8 and show the method of extracting needed parameters from the
21cmFAST tool. To build the model, I first use the Lyman-α emissivity to generate a
Lyman-α photon from a presetting ionization front. Then I propagate the Lyman-α
photon at a distance related to its mean free path and hit it with a hydrogen atom.
The Lyman-α photon will scatter and repeat those steps until it hits either the
boundary of the front of the frequency limit. After the Lyman-α photon hits the
limits and escapes, I record its basic information, such as escaping position, direction,
polarization, and frequency, for further calculation, such as the intensity, polarized
intensity, and power spectrum of the front. The parameters for this model are
blackbody temperature Tbb, front velocity U, and number density of neutral
hydrogen nH. To expand this model into coeval cubes, the model that contains all
the information of the universe under a fixed time, generated by the 21cmFAST tool,
as Tbb is set, I will calculate U and nH from the coeval data boxes.
The source code can be found at https://github.com/SourceYang/Lyman-alpha
Description
Keywords
Astrophysics, Reionization, Lyman-alpha emission, Monte Carlo, Polarization