A novel JEAnS analysis of the Fornax dwarf using evolutionary algorithms: mass follows light with signs of an off-centre merger

Understand

Dwarf galaxies, among the most dark matter dominated structures of our universe, are excellent test-beds for dark matter theories.

• Unfortunately, mass modelling of these systems suffers from the well documented mass-velocity anisotropy degeneracy.
• For the case of spherically symmetric systems, we describe a method for non-parametric modelling of the radial and tangential velocity moments.
• The method is a numerical velocity anisotropy "inversion", with parametric mass models, where the radial velocity dispersion profile, $\sigma_{\mathrm{rr}}^2$ is modeled as a B-spline, and the optimization is a three step process that consists of: (i) an Evolutionary modelling to determine the mass model form and the best B-spline basis to represent $\sigma_{\mathrm{rr}}^2$; (ii) an optimization of the smoothing parameters; (iii) a Markov chain Monte Carlo analysis to determine the physical parameters.