Thermal and reionization history within a large-volume semi-analytic galaxy formation simulation
Abstract
We predict the 21-cm global signal and power spectra during the Epoch of Reionization using the MERAXES semi-analytic galaxy formation and reionization model, updated to include X-ray heating and thermal evolution of the intergalactic medium. Studying the formation and evolution of galaxies together with the reionization of cosmic hydrogen using semi-analytic models (such as M ERAXES) requires N-body simulations within large volumes and high-mass resolutions. For this, we use a simulation of side-length 210 h-1 Mpc with 43203 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 ~1012). Using this augmented simulation, we explore the impact of mass resolution on the predicted reionization history as well as the impact of X-ray heating on the 21-cm global signal and the 21-cm power spectra. We also explore the cosmic variance of 21-cm statistics within 703 h-3 Mpc3 sub-volumes. 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 2-4 at k ~ 0.1-0.4 Mpc-1 due to the non-Gaussian nature of the 21-cm signal. To our knowledge, this work represents the first model of both reionization and galaxy formation which resolves low-mass atomically cooled galaxies while simultaneously sampling sufficiently large scales necessary for exploring the effects of X-rays 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:
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- galaxies: evolution;
- galaxies: high redshift;
- dark ages;
- reionization;
- first stars;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- 17 pages, 13 figures, revised and MNRAS accepted version