Predictive model of fermionic dark matter halos with a quantum core and an isothermal atmosphere

TL;DR

This paper presents a thermodynamical model of fermionic dark matter halos featuring a quantum core and an isothermal atmosphere, explaining galaxy rotation curves and addressing the core-cusp problem.

Contribution

It introduces a new finite-temperature model of fermionic dark matter halos with a core-halo structure derived from maximum entropy principles.

Findings

Quantum core prevents gravitational collapse.

Model reproduces flat galaxy rotation curves.

Addresses the core-cusp problem of cold dark matter.

Abstract

We develop a thermodynamical model of fermionic dark matter halos at finite temperature. Statistical equilibrium states may be justified by a process of violent collisionless relaxation in the sense of Lynden-Bell or from a collisional relaxation of nongravitational origin if the fermions are self-interacting. The most probable state (maximum entropy state) generically has a "core-halo" structure with a quantum core (fermion ball) surrounded by an isothermal atmosphere. The quantum core is equivalent to a polytrope of index $n=3/2$. The Pauli exclusion principle creates a quantum pressure that prevents gravitational collapse and solves the core-cusp problem of the cold dark matter model. The isothermal atmosphere (which is similar to the NFW profile of cold dark matter) accounts for the flat rotation curves of the galaxies at large distances. We numerically solve the equation of hydrostatic equilibrium with the Fermi-Dirac equation of state and determine the density profiles and rotation curves of fermionic dark matter halos.