Axionic dark matter halos in the gravitational field of baryonic matter

Abstract

We consider a dark matter halo (DMH) of a spherical galaxy as a Bose–Einstein condensate (BEC) of the ultra-light axions (ULA) interacting with the baryonic matter. In the mean-field (MF) 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) [Formula: see text] is the ratio of baryon and axion total mases and (ii) [Formula: see text] is 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, [Formula: see text] of DMH as a function of [Formula: see text] and [Formula: see text] and obtained an analytical approximation for [Formula: see text].