A Universal Profile for Stacked Filaments from Cold Dark Matter Simulations

TL;DR

This paper introduces a universal four-parameter model for the dark matter density profiles of stacked filaments connecting galaxy groups, validated across various redshifts, lengths, and masses, aiding observational interpretation.

Contribution

It presents a new universal functional form for stacked filament profiles from dark matter simulations, with parameters that are largely redshift-independent and scale with filament length.

Findings

The four-parameter model fits the simulation data well up to 20 cMpc/h.

Scale radii are approximately independent of redshift but increase with filament length.

Measured filament mass scaling is slightly shallower than theoretical predictions.

Abstract

We study the stacked filaments connecting group-mass halo pairs, using dark-matter-only N-body simulations. We calculate the dark matter over-density profile of these stacked filaments at different redshifts as a function of the distance perpendicular to the filament axis. A four-parameter universal functional form, including three comoving scale radii and one amplitude parameter (core density), provides a good fit out to a radius of 20 cMpc/h for stacked filaments over a range of redshifts, lengths and masses. The scale radii are approximately independent of redshift but increase as power-laws with the comoving filament length. Lastly, we compare the scaling of the filament mass measured directly from the simulations to the predicted scaling from the halo-halo-matter three-point correlation function as a function of redshift and of the mass of the halo pairs. We find that both measured scalings are similar to, but somewhat shallower than the predictions, by 10% and 30%, respectively. These results provide a template to interpret present and upcoming observational results based on stacking, for example, weak lensing, thermal and kinetic Sunyaev-Zel'dovich, or X-ray observations.