Phenomenology and Astrophysics of Gravitationally-Bound Condensates of Axion-Like Particles

Bosonic ultra-light dark matter (ULDM) would form cored density distributions at the center of galaxies. These cores, seen in numerical simulations, admit analytic description as the lowest energy bound state solution ("soliton") of the Schroedinger-Poisson equations. Numerical simulations of ULDM galactic halos found empirical scaling relations between the mass of the large-scale host halo and the mass of the central soliton. We discuss how the simulation results of different groups can be understood in terms of the basic properties of the soliton. Importantly, simulations imply that the energy per unit mass in the soliton and in the virialised host halo should be approximately equal. This relation lends itself to observational tests, because it predicts that the peak circular velocity, measured for the host halo in the outskirts of the galaxy, should approximately repeat itself in the central region. Contrasting this prediction to the measured rotation curves of well-resolved near-by galaxies, we show that ULDM in the mass range m ∼ (10 −22 ÷ 10 −21 ) eV, which has been invoked as a possible solution to the small-scale puzzles of ΛCDM, is in tension with the data. We suggest that a dedicated analysis of the Milky Way inner gravitational potential could probe ULDM up to m 10 −19 eV.

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“…However, there is another way to express Eq. (34). The core mass of a χ λ soliton is related to its total mass via M cλ ≈ 0.236M λ .…”

Section: Soliton Properties: Analytic Considerationsmentioning

confidence: 99%

“…On the other hand, γm can be associated with the chemical potential of ULDM particles in the soliton (see e.g. [34] and references therein). This may appear to hint that Eq.…”

Section: Commentsmentioning

confidence: 99%

Galactic rotation curves versus ultralight dark matter: Implications of the soliton-host halo relation

et al. 2018

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“…Using the variational analysis of Section 2, we can estimate the chemical potential as a function of the rescaled radius ρ (see e.g. [98]):…”

Section: Decaymentioning

confidence: 99%

Stability of condensed fuzzy dark matter halos

Eby

Leembruggen

Surányi

et al. 2018

J. Cosmol. Astropart. Phys.

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Stability properties of gravitationally bound condensates composed of ultralight axionic FuzzyDark Matter (FDM) are studied. Previous work has shown that astrophysical collisions could make self-gravitating condensates structurally unstable, making them prone to collapse and decay; in the context of FDM, we reexamine the relevant timescales using the time-dependent variational method. We show that FDM condensates can be made unstable through gravitational interactions with central black holes, for black hole masses in a phenomenologically relevant range. Instability could also be stimulated by galaxy collisions. The subsequent decay takes place over a period lasting as long as many thousands of years. We also discuss the possible relevance of FDM condensates to understanding the composition of Ultracompact Dwarf (UCD) Galaxies. Future observation of extremely massive black holes in the central regions of UCDs can constrain this interpretation.

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Phenomenology and Astrophysics of Gravitationally-Bound Condensates of Axion-Like Particles

Abstract: I also thank my family, for providing encouragement throughout this process; where friendship is fragile, family is robust, and I thank them for their unwavering support.

Cited by 2 publications

References 153 publications

Galactic rotation curves versus ultralight dark matter: Implications of the soliton-host halo relation

Galactic rotation curves versus ultralight dark matter: Implications of the soliton-host halo relation

Stability of condensed fuzzy dark matter halos

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