# Bar-Halo Friction in Galaxies III: Particle Number Requirements for Simulations

## TL;DR

This study investigates the particle number requirements in N-body simulations of dark matter halo interactions with galactic bars, finding that standard particle counts are sufficient and challenging previous claims of the need for extremely high particle numbers.

## Contribution

The paper demonstrates that typical N-body simulation particle numbers are adequate for modeling bar-halo interactions, countering prior assertions that much higher counts are necessary.

## Key findings

- Simulation results show no dependence on particle number within standard ranges.
- Field and grid methods yield similar results, confirming robustness.
- The suggested high particle number by Weinberg & Katz is unnecessary.

## Abstract

The question whether the dark matter halo density in the centers of galaxies could be changed through interactions with a rotating bar in the baryonic disk is of considerable current interest. While N-body simulations have been used to address this question, it has also been claimed that results from such simulations cannot be trusted. Based on a perturbative treatment of resonant exchanges between orbits and a rotating perturbation, Weinberg & Katz contend that N-body simulations of this process will not reveal the continuum result unless many more than the usual numbers of particles are employed. Here I report a study designed to examine their contention, finding results that show no dependence on the number of particles over the range usually employed up to that advocated by these authors. I show that my results are independent of all numerical parameters, and that field methods perform equally with grid methods in this respect. I also identify the reasons that the required particle number suggested by Weinberg & Katz is excessive.

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Source: https://tomesphere.com/paper/0704.1047