Constraints on the inner density profile of dark-matter haloes from weak gravitational lensing

TL;DR

This paper develops two linear filtering methods using weak gravitational lensing data to accurately estimate the inner density slope of dark-matter halos, accounting for degeneracies with halo concentration.

Contribution

The paper introduces new linear filtering techniques to constrain the inner density profile of dark-matter halos from weak lensing data, including a combined parameter P1 that mitigates degeneracies.

Findings

Inner slope α can be constrained to ~15% with known concentration.

Without known concentration, α can be constrained to less than 30%.

Stacking signals from multiple halos improves profile constraints.

Abstract

We construct two linear filtering techniques based on weak gravitational lensing to constrain the inner slope $\alpha$ of the density profile of dark-matter halos. Both methods combine all available information into an estimate of this single number. Under idealised assumptions, $\alpha$ is constrained to ~15% if the halo concentration c is known, and to < 30% if not. We argue that the inevitable degeneracy between density-profile slope and halo concentration cannot be lifted under realistic conditions, and show by means of Fisher-matrix methods which linear combination of $\alpha$ and c is best constrained by our filtering of lensing data. This defines a new parameter, called P1, which is then constrained to ~15% for a single massive halo. If the signals of many halos can be stacked, their density profiles should thus be well constrained by the linear filters proposed here with the advantagebe insensitive to the cluster substructures.