Self-consistent construction of virialized wave dark matter halos

Summary

Using C++ and MPI, we solve the Schrödinger-Poisson equation numerically by treating the wavefunction as composed of noninteracting eigenstates and assigning their amplitudes based on a distribution function, assuming spherically symmetric. This method provides a way to construct Milky Way-sized wave dark matter halos.

Abstract

Wave dark matter ($\psi$DM), which satisfies the Schrödinger-Poisson equation, has recently attracted substantial attention as a possible dark matter candidate. Numerical simulations have, in the past, provided a powerful tool to explore this new territory of possibility. Despite their successes in revealing several key features of 𝜓⁢DM, further progress in simulations is limited, in that cosmological simulations so far can only address formation of halos below $\sim2 \times 10^{11}  M_{\odot}$ and substantially more massive halos have become computationally very challenging to obtain. For this reason, the present work adopts a different approach in assessing massive halos by constructing wave-halo solutions directly from the wave distribution function. This approach bears certain similarities with the analytical construction of the particle-halo (cold dark matter model). Instead of many collisionless particles, one deals with one single wave that has many noninteracting eigenstates. The key ingredient in the wave-halo construction is the distribution function of the wave power, and we use several halos produced by structure formation simulations as templates to determine the wave distribution function. Among different models, we find the fermionic King model presents the best fits and we use it for our wave-halo construction. We have devised an iteration method for constructing the nonlinear halo and demonstrate its stability by three-dimensional simulations. A Milky Way–sized halo has also been constructed, and the inner halo is found to be flatter than the NFW profile. These wave-halos have small-scale interferences both in space and time producing time-dependent granules. While the spatial scale of granules varies little, the correlation time is found to increase with radius by 1 order of magnitude across the halo.

Citation

@article{lin2018self,
  title={Self-consistent construction of virialized wave dark matter halos},
  author={Lin, Shan-Chang and Schive, Hsi-Yu and Wong, Shing-Kwong and Chiueh, Tzihong},
  journal={Physical Review D},
  volume={97},
  number={10},
  pages={103523},
  year={2018},
  publisher={APS}
}