Physics of the Dark Universe 28 (2020) 100503 Contents lists available at ScienceDirect Physics of the Dark Universe journal homepage: www.elsevier.com/locate/dark Dynamical evidence of a dark solitonic core of 10 9 M ⊙ in the milky way Ivan De Martino a,∗ , Tom Broadhurst a,b,c , S.-H. Henry Tye d , Tzihong Chiueh e,f , Hsi-Yu Schive g a Donostia International Physics Center (DIPC), 20018 Donostia-San Sebastian (Gipuzkoa), Spain b Department of Theoretical Physics, University of the Basque Country UPV/EHU, E-48080 Bilbao, Spain c Ikerbasque, Basque Foundation for Science, E-48011 Bilbao, Spain d Institute for Advanced Study and Department of Physics, Hong Kong University of Science and Technology, Hong Kong e Department of Physics, National Taiwan University, Taipei 10617, Taiwan f National Center for Theoretical Sciences, National Taiwan University, Taipei 10617, Taiwan g National Center for Supercomputing Applications, Urbana, IL 61801, USA article info Article history: Received 14 November 2019 Received in revised form 29 January 2020 Accepted 9 February 2020 Keywords: Cosmological theory Dark matter Axion Particle physics Galaxy abstract A wavelike solution for the non-relativistic universal dark matter (wave-DM) is rapidly gaining interest, following pioneering simulations of cosmic structure as an interference pattern of coherently oscillating bosons. A prominent solitonic standing wave is predicted at the center of every galaxy, representing the ground state solution of the coupled Schrödinger–Poisson equations, and it has been identified with the wide, kpc scale dark cores of common dwarf-spheroidal galaxies. A denser soliton is predicted for Milky Way sized galaxies where momentum is higher, so the de Broglie scale of the soliton is smaller, ≃ 100 pc, of mass ≃ 10 9 M ⊙ . Here we show the central motion of bulge stars in the Milky Way implies the presence of such a dark core, where the velocity dispersion rises inversely with radius to a maximum of ≃ 130 km/s, corresponding to an excess central mass of ≃ 1.5 × 10 9 M ⊙ within ≃ 100 pc, favoring a boson mass of ≃ 10 −22 eV. This quantitative agreement with such a unique and distinctive prediction is therefore strong evidence for a light bosonic solution to the long standing Dark Matter puzzle. © 2020 Elsevier B.V. All rights reserved. 1. Introduction The nature of the Dark Matter (DM) is understood to require new physics, as baryonic matter described by standard particle physics is found to contribute only 17% of the cosmic mass density [1,2]. We know DM is non-relativistic, to the earliest limits of observation, otherwise the Cosmic Microwave Back- ground (CMB) and the large scale distribution of galaxies would be featureless on small scales. In addition, collisions between galaxy clusters show no detectable self-interaction other than gravity [3,4]. However, the composition of this collisionless, ‘‘Cold Dark Matter’’ (CDM) is unclear, particularly with the contin- ued laboratory absence of any new heavy particles to stringent limits [5]. Furthermore, predictions of CDM are problematic on small scales, < 10 kpc, in relation to low mass galaxies. An interesting alternative to CDM is dark matter composed of an extremely light boson (m ψ ∼ 10 −22 eV), sometimes called Fuzzy Dark ∗ Corresponding author. E-mail addresses: ivan.demartino@dipc.org (I. De Martino), tom.j.broadhurst@gmail.com (T. Broadhurst), iastye@ust.hk (S.-H. Henry Tye), chiuehth@phys.ntu.edu.tw (T. Chiueh), hyschive@gmail.com (H.-Y. Schive). Matter (FDM) [6–10]. Since de Broglie wavelength of these light bosons is of order λ dB ∼ 1 kpc, the physics differs fundamen- tally from CDM on scales below λ dB . The uncertainty principle means bosons cannot be confined within this de Broglie scale, naturally suppressing dwarf galaxy formation below 10 10 M ⊙ . So the question arises, what replaces the cuspy inner profile of CDM within 10 kpc? It turns out that there is a rich, unforeseen granular sub-structure on the de-Broglie scale, as revealed by the simulations [11], with qualitative [12] and quantitative sup- port [13] by subsequent independent simulations. Wave-DM cos- mological simulations of [11,14] that evolve classical scalar fields obeying the non-relativistic Schrödinger–Poisson equations [6– 8], under the simplest assumption of negligible self-interaction other than gravity, produce halos with a central core that is a stationary, minimum-energy solution, sometimes called a soliton, surrounded by a granular envelope resembling a CDM halo when averaged azimuthally [11,14]. With the boson mass as the only free parameter, the soliton solution has a scaling symmetry, thus forming a one parameter family of solutions. We shall refer to FDM with this one-parameter solitonic core as wave-DM or ‘‘ψ DM’’. Simulations with a wide dynamical range from the de Broglie wavelength to cosmological scale must rely on some simplifying https://doi.org/10.1016/j.dark.2020.100503 2212-6864/© 2020 Elsevier B.V. All rights reserved.