Comparison of weak lensing by NFW and Einasto halos and systematic errors

TL;DR

This paper compares weak lensing predictions using NFW and Einasto halo profiles, highlighting potential systematic errors in mass and concentration estimates when the wrong profile is assumed, especially for massive clusters.

Contribution

It quantifies the systematic errors in weak lensing analyses caused by using NFW profiles instead of Einasto profiles and suggests methods to distinguish between them observationally.

Findings

NFW fits can over- or underestimate halo masses and concentrations by ~10% for very massive halos.

Misfitting NFW profiles affects the observed mass-concentration relation.

Deep observations or stacking shear profiles can differentiate between NFW and Einasto halos.

Abstract

Recent N-body simulations have shown that Einasto radial profiles provide the most accurate description of dark matter halos. Predictions based on the traditional NFW functional form may fail to describe the structural properties of cosmic objects at the percent level required by precision cosmology. We computed the systematic errors expected for weak lensing analyses of clusters of galaxies if one wrongly models the lens density profile. Even though the NFW fits of observed tangential shear profiles can be excellent, viral masses and concentrations of very massive halos (>~ 10^{15}M_Sun/h) can be over- and underestimated by ~10 per cent, respectively. Misfitting effects also steepen the observed mass-concentration relation, as observed in multi-wavelength observations of galaxy groups and clusters. Based on shear analyses, Einasto and NFW halos can be set apart either with deep observations of exceptionally massive structures (>~ 2\times10^{15}M_Sun/h) or by stacking the shear profiles of thousands of group-sized lenses (>~ 10^{14}M_Sun/h).