Halo mass and weak galaxy-galaxy lensing profiles in rescaled cosmological $N$-body simulations

TL;DR

This paper extends a cosmology-rescaling algorithm for N-body simulations to improve predictions of dark matter halo profiles, achieving high accuracy on intra-halo scales and demonstrating its utility for galaxy group mass estimation.

Contribution

The authors enhance the rescaling method by incorporating models for concentration-mass-redshift relations, improving accuracy on intra-halo scales in cosmological simulations.

Findings

Predictions for median density profiles are accurate within 5% for certain halo masses and radii.

Accuracy degrades to about 20% at larger radii due to splashback radius modeling issues.

Residuals decrease to below 2% for current cosmological parameter variations.

Abstract

We investigate 3D density and weak lensing profiles of dark matter haloes predicted by a cosmology-rescaling algorithm for $N$-body simulations. We extend the rescaling method of Angulo & White (2010) and Angulo & Hilbert (2015) to improve its performance on intra-halo scales by using models for the concentration-mass-redshift relation based on excursion set theory. The accuracy of the method is tested with numerical simulations carried out with different cosmological parameters. We find that predictions for median density profiles are more accurate than $\sim 5\,\%$ for haloes with masses of $10^{12.0} - 10^{14.5} h^{-1}\,M_{\odot}$ for radii $0.05 < r/r_{200\text{m}} < 0.5$, and for cosmologies with $\Omega_\text{m} \in [0.15,\,0.40]$ and $\sigma_8 \in [0.6,\,1.0]$. For larger radii, $0.5 < r/r_{200\text{m}} < 5$, the accuracy degrades to $\sim20\,\%$, due to inaccurate modelling of the cosmological and redshift dependence of the splashback radius. For changes in cosmology allowed by current data, the residuals decrease to $\lesssim2\,\%$ up to scales twice the virial radius. We illustrate the usefulness of the method by estimating the mean halo mass of a mock galaxy group sample. We find that the algorithm's accuracy is sufficient for current data. Improvements in the algorithm, particularly in the modelling of baryons, are likely required for interpreting future (dark energy task force stage IV) experiments.