Prediction of the 21-cm signal from reionization: comparison between 3D and 1D radiative transfer schemes

TL;DR

This study compares 1D and 3D radiative transfer simulations of the epoch of reionization, finding that 1D schemes can produce results comparable to 3D with less computational cost, useful for parameter exploration.

Contribution

It demonstrates that 1D radiative transfer schemes can closely match 3D results in reionization simulations, offering a faster alternative for analysis.

Findings

Ionization and 21-cm maps are very similar between schemes.

Power spectrum differences are within 10% throughout reionization.

grizzly outperforms some semi-numerical methods in accuracy.

Abstract

Three-dimensional radiative transfer simulations of the epoch of reionization can produce realistic results, but are computationally expensive. On the other hand, simulations relying on one-dimensional radiative transfer solutions are faster but limited in accuracy due to their more approximate nature. Here, we compare the performance of the reionization simulation codes grizzly and C2-ray which use 1D and 3D radiative transfer schemes respectively. The comparison is performed using the same cosmological density fields, halo catalogues and source properties. We find that the ionization maps, as well as the 21-cm signal maps from these two simulations are very similar even for complex scenarios which include thermal feedback on low mass halos. The comparison between the schemes in terms of the statistical quantities such as the power spectrum of the brightness temperature fluctuation agree with each other within 10% error throughout the entire reionization history. grizzly seems to perform slightly better than the semi-numerical approaches considered in Majumdar et al. (2014) which are based on the excursion set principle. We argue that grizzly can be efficiently used for exploring parameter space, establishing observations strategies and estimating parameters from 21-cm observations.