An efficient hybrid method to produce highresolution largevolume dark matter simulations for semianalytic models of reionization
Abstract
Resolving faint galaxies in large volumes is critical for accurate cosmic reionization simulations. While less demanding than hydrodynamical simulations, semianalytic reionization models still require very large Nbody simulations in order to resolve the atomic cooling limit across the whole reionization history within box sizes ${\gtrsim}100 \, h^{1}\, \rm Mpc$ . To facilitate this, we extend the mass resolution of Nbody simulations using a Monte Carlo algorithm. We also propose a method to evolve positions of Monte Carlo haloes, which can be an input for semianalytic reionization models. To illustrate, we present an extended halo catalogue that reaches a mass resolution of $M_\text{halo} = 3.2 \times 10^7 \, h^{1} \, \text{M}_\odot$ in a $105 \, h^{1}\, \rm Mpc$ box, equivalent to an Nbody simulation with ∼6800^{3} particles. The resulting halo mass function agrees with smaller volume Nbody simulations with higher resolution. Our results also produce consistent twopoint correlation functions with analytic halo bias predictions. The extended halo catalogues are applied to the MERAXES semianalytic reionization model, which improves the predictions on stellar mass functions, star formation rate densities, and volumeweighted neutral fractions. Comparison of highresolution largevolume simulations with both smallvolume and lowresolution simulations confirms that both lowresolution and smallvolume simulations lead to reionization ending too rapidly. Lingering discrepancies between the star formation rate functions predicted with and without our extensions can be traced to the uncertain contribution of satellite galaxies.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 October 2020
 DOI:
 10.1093/mnras/staa3261
 arXiv:
 arXiv:2007.14624
 Bibcode:
 2020MNRAS.500..493Q
 Keywords:

 methods: numerical;
 galaxies: highredshift;
 dark ages;
 reionization;
 first stars;
 Astrophysics  Astrophysics of Galaxies;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 15 pages, 15 figures. Accepted for publication in MNRAS