Understanding the Core-Halo Relation of Quantum Wave Dark Matter from 3D Simulations

Abstract

We examine the nonlinear structure of gravitationally collapsed objects that form in our simulations of wavelike cold dark matter (ψDM), described by the Schrödinger-Poisson (SP) equation with a particle mass ∼ 10 −22 eV. A distinct gravitationally self-bound solitonic core is found at the center of every halo, with a profile quite different from cores modeled in the warm or self-interacting dark matter scenarios. Furthermore, we show that each solitonic core is surrounded by an extended halo composed of large fluctuating dark matter granules which modulate the halo density on a scale comparable to the diameter of the solitonic core. The scaling symmetry of the SP equation and the uncertainty principle tightly relate the core mass to the halo specific energy, which, in the context of cosmological structure formation, leads to a simple scaling between core mass (Mc) and haloh , where a is the cosmic scale factor. We verify this scaling relation by (i) examining the internal structure of a statistical sample of virialized halos that form in our 3D cosmological simulations, and by (ii) merging multiple solitons to create individual virialized objects. Sufficient simulation resolution is achieved by adaptive mesh refinement and graphic processing units acceleration. From this scaling relation, present dwarf satellite galaxies are predicted to have kpc sized cores and a minimum mass of ∼ 10 8 M⊙, capable of solving the small-scale controversies in the cold dark matter model. Moreover, galaxies of 2 × 10 12 M⊙ at z = 8 should have massive solitonic cores of ∼ 2 × 10 9 M⊙ within ∼ 60 pc. Such cores can provide a favorable local environment for funneling the gas that leads to the prompt formation of early stellar spheroids and quasars.PACS numbers: 03.75. Lm, 95.35.+d, 98.56.Wm, 98.62.Gq Accumulating evidences suggest that the Universe contains ∼ 26% dark matter [1] which interacts primarily through self-gravity. Dark matter comprising very light bosons with a mass m ψ ∼ 10 −22 eV has been recognized as a viable means of suppressing low mass galaxies and providing cored profiles in dark matter dominated galaxies [2,3]. Interestingly, this boson mass scale can naturally arise in a non-QCD axion model [4], lending support for the very light boson. The relative deficiency of the observed number of low-mass galaxies is a major problem for standard cold dark matter (CDM) [5][6][7], for which a steeply rising mass function is predicted [8]. Furthermore, the dwarf spheroidal galaxies [9-20] and low surface brightness galaxies [21,22] are generally inferred to have large flat cores of dark matter, at odds with the singular cores required by standard CDM [23,24]. Complicated baryonic physics such as supernova feedback is required to solve both issues in the CDM paradigm [25][26][27][28][29][30][31][32][33][34].Extremely light bosonic dark matter can be assumed to be non-thermally generated and described by a single coherent wave function [2,[35][36][37][38], which we term ψDM. Here solutions to both the missing-satellite and ...

Perturbations of ultralight vector field dark matter

“…More concretely the comoving de Broglie wavelength is λ deBroglie = (Hma) −1/2 [43]. This means that since it is not possible to localize the DM particle on scales smaller than λ deBroglie , structure formation is suppressed on those small scales [44][45][46][47]. Thus, in this kind of models, we have two different regimes for perturbations.…”

Brief History of Ultra-light Scalar Dark Matter Models

“…The SFDM could solve the cusp problem [17,31,32,32,66,[66][67][68] because of the boundary condition for the SPE at the halo center. There are many works explaining the rotation curves of dwarf [17,23,69], and large galaxies [29,43,[70][71][72][73][74][75][76][77][78] in this model. By fitting RCs one can obtain the scalar field mass m ∼ 10 −22 eV, and interestingly the SFDM with this mass range can resolve many of the small scale problems of CDM models.…”

Scalar field (wave) dark matter

“…The size of the MSH is determined by the most excited state that accurately fits the RC for large radii, excited states are distributed to larger radii than the ground state, and in contrast to the halo with single state there are MSHs that are stable under finite perturbations provided the ground state in the final halo configuration has enough mass to stabilize the coexisting state 3,72 . Although there are still uncertainties in the stability of the MSHs, the appearance of bosons in excited states seems to be a straightforward consequences of quantum interference triggered by halo mergers as confirmed recently in 63 , and possibly the internal evolution of the halo. Moreover, initial fluctuations that grow due to the cosmological expansion of the universe eventually separate from it and start collapsing due to its own gravity, at this time (known as turnaround) the halo can have a number of psyons that are in different states which depend on the the local environment.…”