The Dark Matter Density Profile of the Fornax Dwarf

TL;DR

This study uses axisymmetric Schwarzschild models to analyze the dark matter density profile of the Fornax dwarf galaxy, finding evidence for a cored profile over a cuspy one and setting limits on an intermediate-mass black hole.

Contribution

It introduces a no-assumption Schwarzschild modeling approach to determine the dark matter profile of Fornax, favoring cored over cuspy models and constraining black hole mass.

Findings

Cored dark matter profile fits better than cuspy models.

Uniform density core of approximately 1.6 x 10^-2 M_sun/pc^3.

Upper limit on black hole mass at 3.2 x 10^4 M_sun.

Abstract

We construct axisymmetric Schwarzschild models to measure the mass profile of the local group dwarf galaxy Fornax. These models require no assumptions to be made about the orbital anisotropy of the stars, as is the case for commonly used Jeans models. We test a variety of parameterizations of dark matter density profiles and find cored models with uniform density rho_c = (1.6 +/- 0.1) x 10^-2 M_sun pc^-3 fit significantly better than the cuspy halos predicted by cold dark matter simulations. We also construct models with an intermediate-mass black hole, but are unable to make a detection. We place a 1-sigma upper limit on the mass of a potential intermediate-mass black hole at M_BH < 3.2 x 10^4 M_sun.