Fuzzy Dark Matter and Dark Matter Halo Cores

Abstract

Whereas cold dark matter (CDM) simulations predict central dark matter cusps with densities that diverge as ρ(r)∼ 1/r observations often indicate constant density cores with finite central densities ρ 0 and a flat density distribution within a core radius r 0 . This paper investigates whether this core-cusp problem can be solved by fuzzy dark matter (FDM), a hypothetical particle with a mass of order m≈10 −22 eV and a corresponding de Broglie wavelength on astrophysical scales. We show that galaxies with CDM halo virial masses M vir ≤ 10 11 M ⊙ follow two core scaling relations. In addition to the well known universal core column density Σ 0 ≡ ρ 0 ×r 0 = 75 M ⊙ pc −2 core radii increase with virial masses as r 0 ∼ M γ vir with γ of order unity. Using the simulations by Schive et al. ( 2014) we demonstrate that FDM can explain the r 0 -M vir scaling relation if the virial masses of the observed galaxy sample scale with formation redshift z as M vir ∼(1+z) −0.4 . The observed constant Σ 0 is however in complete disagreement with FDM cores which are characterised by a steep dependence Σ 0 ∼r −3 0 , independent of z. More highresolution simulations are now required to confirm the Schive et al. simulations and explore especially the transition region between the soliton core and the surrounding halo. If these results hold, FDM can be ruled out as the origin of observed dark matter cores and other physical processes are required to account for their formation.

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

“…For example, a soliton core is found to fit very well the cores observed in some dwarf galaxies, which in turn have been used to constrain, or even determine, the mass of the light boson assuming that the formation mechanism of such cores is solely due to the phenomenology of ULAs or FDM Marsh & Pop 2015;Calabrese & Spergel 2016;González-Morales et al 2017;Bozek et al 2015). On the other hand, Burkert (2020) recently argued that dark matter cores previously predicted by cosmological simulations involving this class of models are inconsistent with observations if FDM dark halos form following the classical hierarchical paradigm.…”

“…Salucci & Burkert 2000;Burkert 2015;Kormendy 2015;). This relation can provide strong constraints on any core formation mechanism and, in Burkert (2020), it was recently argued that this represents a challenge to the FDM model to explain the observed cores. In Fig.…”

Wave Dark Matter

“…Some experiments measure φ by searching for a time varying magnetic flux produced by the oscillating axion in the presence of an external magnetic field, such as ABRACADABRA (Kahn et al 2016, Ouellet et al 2019. Others are sensitive to ∇φ, such as CASPEr (Graham & Rajendran 2013, Budker et al 2014 or spin pendulum experiments (Terrano et al 2019). The idea is to measure the spin precession around the direction picked out by ∇φ, using the axion-fermion coupling (Equation 9).…”

Consequences for the Scalar Field Dark Matter model from The McGaugh Observed-Baryon Acceleration Correlation

“…Indeed, the fact that this correlation has been robustly established by simulations offers a unique opportunity to understand and extend the correlation by considering novel physical effects such as the addition of more matter contributions in the total halo. One of the problems that is currently becoming more and more evident in this model is the fact that the cosmological simulations of galaxy formation do not seem to agree with the results of a constant surface density, as suggested by Burkert (2015), Donato et al (2009), Salucci and Burkert (2000), Spano et al (2008), in such case it has been claimed that the SFDM is not able to correctly describe a realistic core formation mechanism in galaxies (see for example Burkert 2020, Mina et al 2020. However, most of the works in the model as well as the conclusions we have mentioned until now have been commonly obtained by means of DM-only simulation results.…”