Fitting functions for dark matter density profiles

TL;DR

This paper introduces a unified parameterization for dark matter and elliptical galaxy density profiles, showing that the Einasto profile naturally emerges as a limit of Zhao's double power-law models, blurring distinctions between different halo models.

Contribution

It presents a unified fitting function framework that encompasses the Einasto profile as a limit of Zhao's models, suggesting minimal qualitative differences between halo models.

Findings

Einasto profile is a natural limit of Zhao's double power-law profiles.

No qualitative difference between halo models fitted by Einasto or NFW.

Distinguishing models requires high-resolution simulations and precise fittings.

Abstract

We present a unified parameterization of the fitting functions suitable for density profiles of dark matter haloes or elliptical galaxies. A notable feature is that the classical Einasto profile appears naturally as the continuous limiting case of the cored subfamily amongst the double power-law profiles of Zhao (1996). Based on this, we also argue that there is basically no qualitative difference between halo models well-fitted by the Einasto profile and the standard NFW model. This may even be the case quantitatively unless the resolutions of simulations and the precisions of fittings are sufficiently high to make meaningful distinction possible.