Gravitational lensing properties of isothermal universal halo profile

TL;DR

This paper models galaxy halos as a combination of isothermal and NFW profiles, providing new formulas for lensing signals and showing it predicts stronger lensing effects than traditional models, aiding in distinguishing halo structures.

Contribution

It introduces a combined halo profile model with exact lensing expressions, enhancing understanding of gravitational lensing signatures of galaxy halos.

Findings

Combined profile produces higher order lensing signals at small radii

More efficient in generating strong lensing events

Distinguishing halo profiles requires combined lensing constraints

Abstract

N-body simulations predict that dark matter halos with different mass scales are described by a universal model, the Navarro-Frenk-White (NFW) density profiles. As a consequence of baryonic cooling effects, the halos will become more concentrated, and similar to an isothermal sphere over large range in radii ($\sim 300$ $h^{-1}$kpc). The singular isothermal sphere model however has to be truncated artificially at large radii since it extends to infinity. We model a massive galaxy halo as a combination of an isothermal sphere and an NFW density profile. We give an approximation for the mass concentration at different baryon fractions and present exact expressions for the weak lensing shear and flexion for such a halo. We compare the lensing properties with a Singular Isothermal Sphere and NFW profiles. We find that the combined profile can generate higher order lensing signals at small radii and is more efficient in generating strong lensing events. In order to distinguish such a halo profile from the SIS or NFW profiles, one needs to combine strong and weak lensing constraints on small and large radii.