Axionic Dark Matter Halos in the Gravitational Field of Baryonic Matter

TL;DR

This paper models axionic dark matter halos in galaxies as Bose-Einstein condensates interacting with baryonic matter, deriving equations and numerical methods to analyze their size and structure.

Contribution

It introduces a new integro-differential equation for axion halos considering baryonic interaction and extends numerical algorithms to study their ground states.

Findings

Derived the Hartree-Fock type equation for axion halos.

Calculated the characteristic size of dark matter halos as a function of key parameters.

Provided an analytical approximation for the halo size.

Abstract

We consider a dark matter halo (DMH) of a spherical galaxy as a Bose-Einstein condensate of the ultra-light axions interacting with the baryonic matter. In the mean-field limit, we have derived the integro-differential equation of the Hartree-Fock type for the spherically symmetrical wave function of the DMH component. This equation includes two independent dimensionless parameters: (i) \b{eta}- the ratio of baryon and axion total mases and (ii) {\xi}- the ratio of characteristic baryon and axion spatial parameters. We extended our dissipation algorithm for studying numerically the ground state of the axion halo in the gravitational field produced by the baryonic component. We calculated the characteristic size, Xc, of DMH as a function of \b{eta} and {\xi} and obtained an analytical approximation for Xc.