Cosmological Remapping for Efficient Generation of 21 cm Intensity Mapping Mocks

TL;DR

This paper introduces a cosmological remapping technique to efficiently generate 21 cm intensity mapping simulations across different cosmologies, reducing computational costs for large-scale structure studies.

Contribution

The authors develop and validate a remapping method that rescales existing simulations to produce accurate 21 cm mocks for various cosmologies, streamlining simulation workflows.

Findings

Remapping accurately reproduces 21 cm maps for different cosmologies.

The method reduces computational resources compared to full N-body simulations.

Limitations depend on halo mass thresholds and rescaling parameters.

Abstract

We present a novel application of cosmological rescaling, or "remapping," to generate 21 cm intensity mapping mocks for different cosmologies. The remapping method allows for computationally efficient generation of N-body catalogs by rescaling existing simulations. In this work, we employ the remapping method to construct dark matter halo catalogs, starting from the Horizon Run 4 simulation with WMAP5 cosmology, and apply it to different target cosmologies, including WMAP7, Planck18 and Chevallier-Polarski-Linder (CPL) models. These catalogs are then used to simulate 21 cm intensity maps. We use the halo occupation distribution (HOD) method to populate halos with neutral hydrogen (HI) and derive 21 cm brightness temperature maps. Our results demonstrate the effectiveness of the remapping approach in generating cosmological simulations for large-scale structure studies, offering an alternative for testing observational data pipelines and performing cosmological parameter forecasts without the need for computationally expensive full N-body simulations. We also analyze the precision and limitations of the remapping, in light of the rescaling parameters $s$ and $s_m$, as well as the effects of the halo mass and box size thresholds.