Solitons in the dark: non-linear structure formation with fuzzy dark matter

Abstract

We present the results of a full cosmological simulation with the new code SCALAR, where dark matter is in form of fuzzy dark matter, described by a light scalar field with a mass of m B = 2.5 × 10 −22 eV and evolving according to the Schrödinger-Poisson system of equations. In comoving units, the simulation volume is 2.5 h −1 Mpc on a side, with a resolution of 20 h −1 pc at the finest refinement level. We analyse the formation and the evolution of central solitonic cores, which are found to leave their imprints on dark matter density profiles, resulting in shallower central densities, and on rotation curves, producing an additional circular velocity peak at small radii from the center. We find that the suppression of structures due to the quantum nature of the scalar field results in an shallower halo mass function in the low-mass end compared to the case of a ΛCDM simulation, in which dark matter is expected to cluster at all mass scales even if evolved with the same initial conditions used for fuzzy dark matter. Furthermore, we verify the scaling relations characterising the solution to the Schrödinger-Poisson system, for both isolated and merging halos, and we find that they are preserved by merging processes. We characterise each fuzzy dark matter halo in terms of the dimensionless quantity Ξ ∝ |E halo | /M 3 halo and we show that the core mass is tightly linked to the halo mass by the core-halo mass relation M core /M halo ∝ Ξ 1/3 . We also show that the core surface density of the simulated fuzzy dark matter halos does not follow the scaling with the core radius as observed for dwarf galaxies, representing a big challenge for the fuzzy dark matter model as the sole explanation of core formation.

Astrophysical Searches and Constraints on Ultralight Bosonic Dark Matter

“…A second special class of UBDM compact objects is formed by the process of spontaneous symmetry breaking, if this occurs during the normal course of thermal evolution of the Universe (as opposed to during the initial Very recently some authors have even found a different best-fit exponent [98,99], and numerical convergence may also play a part. The issue is not yet resolved at the time of writing.…”

Orbits and adiabatic contraction in scalar field dark matter halos: revisiting the cusp-core problem in dwarf galaxies

“…Almost all of that body of work focuses on FDM with particle mass 𝑚 ∼ (10 −23 − 10 −22 ) eV/𝑐 2 , chosen such that the respective 𝜆 dB ∼ (1 − 10) kpc is large enough to expose the genuine different dynamics of (S)FDM, where quantum wave phenomena, such as coherent states or wave interference, are seen at galactic scales and beyond. More precisely, FDM simulations like those of Schive et al (2014), Schwabe, Niemeyer & Engels (2016), Mocz et al (2017) and Mina, Mota & Winther (2020) have revealed that halos, grown either in a static or expanding background, exhibit a core-envelope structure, where the coherent solitonic halo core is embedded into a highly dynamical halo envelope. Also, certain core-halo scaling relationships have been determined between core and the halo at large, although the results of simulations differ somewhat with respect to the exponents found, which has consequences for other observables, see Padilla et al (2021).…”

Constraints on self-interacting Bose-Einstein condensate dark matter using large-scale observables

“…This type of DM is more generally termed Fuzzy DM (FDM), because these particles can be regarded as "fuzzy" due to the Heisenberg uncertainty principle. Cosmological simulations have shown that FDM halos have solitonic cores, and approaches a NFW-like profile at larger radii [42,44,45,49,59]. Both simulations and cosmological data [3,26,27,29,31,34,57] suggest the mass of the ultra-light scalar particle in the FDM scenario to be around 10 −22 eV.…”