Thermal and reionization history within a largevolume semianalytic galaxy formation simulation
Abstract
We predict the 21cm global signal and power spectra during the Epoch of Reionization using the MERAXES semianalytic galaxy formation and reionization model, updated to include Xray heating and thermal evolution of the intergalactic medium. Studying the formation and evolution of galaxies together with the reionization of cosmic hydrogen using semianalytic models (such as M ERAXES) requires Nbody simulations within large volumes and highmass resolutions. For this, we use a simulation of sidelength 210 h^{1} Mpc with 4320^{3} particles resolving dark matter haloes to masses of $5\times 10^8 \rm{ }h^{1}\, \mathrm{M_\odot }$. To reach the mass resolution of atomically cooled galaxies, thought to be the dominant population contributing to reionization, at z = 20 of $\sim 2\times 10^7 \text{ }h^{1}\, \mathrm{M_\odot }$, we augment this simulation using the DARKFOREST Monte Carlo merger tree algorithm (achieving an effective particle count of ~10^{12}). Using this augmented simulation, we explore the impact of mass resolution on the predicted reionization history as well as the impact of Xray heating on the 21cm global signal and the 21cm power spectra. We also explore the cosmic variance of 21cm statistics within 70^{3} h^{3 }Mpc^{3} subvolumes. We find that the midpoint of reionization varies by Δz ~ 0.8 and that the cosmic variance on the power spectrum is underestimated by a factor of 24 at k ~ 0.10.4 Mpc^{1} due to the nonGaussian nature of the 21cm signal. To our knowledge, this work represents the first model of both reionization and galaxy formation which resolves lowmass atomically cooled galaxies while simultaneously sampling sufficiently large scales necessary for exploring the effects of Xrays in the early Universe.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 April 2023
 DOI:
 10.1093/mnras/stad281
 arXiv:
 arXiv:2210.08910
 Bibcode:
 2023MNRAS.520.3368B
 Keywords:

 galaxies: evolution;
 galaxies: high redshift;
 dark ages;
 reionization;
 first stars;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 17 pages, 13 figures, revised and MNRAS accepted version