Axionlike dark-matter winds driven by galactic baryon redistribution

TL;DR

This paper models axionlike dark matter as a Bose-Einstein condensate in dwarf galaxies, analyzing how baryonic processes induce perturbations that generate small density fluctuations and DM winds, with implications for star formation.

Contribution

It introduces a hydrodynamic model of axionlike DM with baryonic perturbations, exploring their effects on DM density and dynamics in dwarf galaxies, supported by observational data.

Findings

DM density increases by 0.01% due to baryonic perturbations

DM wind velocities reach several meters per second

Metastable excitations decay over 32 million years

Abstract

We examine solutions of the hydrodynamic equations for dark matter (DM) modeled as a Bose-Einstein condensate (BEC) with axionlike interaction, forming a spherically symmetric halo in dwarf galaxies. Small perturbations and decoherence of the BEC DM arise from changes in the gravitational background induced by subgalactic baryonic processes. Focusing on the events in the central region of a galaxy, overlapping with the stable DM core, we consider three scenarios: (i) expansion of a gaseous shell mimicking stellar explosions, (ii) collapse of a shell modeling star formation, and (iii) contraction of a stellar cluster toward the galactic center, driven by dynamical friction within a gaseous shell. Numerical parameters are extracted from observational data for NGC 2366. Our results show central DM density increases of 0.01 percent and DM wind velocities of up to several meters per second. A greater increase in density is observed at lower wind speeds and vice versa. These results raise the question of whether minor DM variations significantly affect star formation. In analyzing the fate of the cumulative impact of baryonic processes, we turn to the quantum excitation model with a discrete spectrum in finite volume. In the inhomogeneous DM halo, including unstable phase, metastable excitations associated with false vacuum states decay over 32 million years. This induces the decay of the system's evolutionary operator. Meanwhile, the Beliaev damping, originating from the decay of stable quasiparticles, emerges in the next order of perturbation.