APS : Soliton Merger Rates and Enhanced Axion Dark Matter Decay

Du, Xiaolong; Escudero, Miguel; Blas, Diego; Pooni, Charis Kaur; Fairbairn, Malcolm; Benson, Andrew; Marsh, David J.E.

doi:10.1103/PhysRevD.109.043019

Article
Report number	arXiv:2301.09769 ; KCL-PH-TH-2023-03 ; CERN-TH-2023-009
Title	Soliton Merger Rates and Enhanced Axion Dark Matter Decay
Author(s)	Du, Xiaolong (Carnegie Inst. Observ. ; UCLA) ; Marsh, David J.E. (King's Coll. London) ; Escudero, Miguel (CERN) ; Benson, Andrew (Carnegie Inst. Observ.) ; Blas, Diego (Barcelona, Autonoma U. ; Barcelona, IFAE) ; Pooni, Charis Kaur (King's Coll. London) ; Fairbairn, Malcolm (King's Coll. London)
Publication	2024-02-08
Imprint	2023-01-23
Number of pages	18
Note	18 pages, 18 figures. Version 2: matches published version. Add an appendix discussing the timescale of axion star merging process due to dynamical friction
In:	Phys. Rev. D 109 (2024) 043019
DOI	10.1103/PhysRevD.109.043019 (publication)
Subject category	hep-ph ; Particle Physics - Phenomenology ; astro-ph.HE ; Astrophysics and Astronomy ; astro-ph.CO ; Astrophysics and Astronomy
Abstract	Solitons are observed to form in simulations of dark matter (DM) halos consisting of bosonic fields. We use the extended Press-Schechter formalism to compute the mass function of solitons, assuming various forms for the relationship between halo mass and soliton mass. We further provide a new calculation of the rate of soliton major mergers. Solitons composed of axion DM are unstable above a critical mass, and decay to either relativistic axions or photons, depending on the values of the coupling constants. We use the computed soliton major merger rate to predict the enhanced DM decay rate due to soliton instability. For certain values of currently allowed axion parameters, the energy injection into the intergalactic medium from soliton decays to photons is comparable to or larger than the energy injection due to core collapse supernovae at $z>10$. A companion paper explores the phenomenology of such an energy injection.
Copyright/License	publication: © 2024-2025 American Physical Society preprint: (License: arXiv nonexclusive-distrib 1.0)

$Energy injection into the intergalactic medium from axion dark matter decay caused by soliton mergers. For comparison, a typical energy scale and redshift for energy injection from Pop-III core-collapse supernovae (CCSNe) is indicated~\cite{Hartwig:2022lon}. For the parameters shown, axion star explosions inject more energy than supernovae. See~\cite{Escudero:2023vgv} for the cosmological implications of such decays.Solid and dashed lines indicate different assumptions for the core-halo mass relation of $\alpha=1/3$ and $\alpha=3/5$.$ $The axion star mass function, $F_S={\rm d}n_S/{\rm d}\ln M_S$ defined by Eq.~\eqref{eqn:star-mf}, using the Sheth-Tormen halo mass function at $z=10$, assuming the core-halo mass relation, Eq.~\eqref{eqn:core-halo}. \emph{Left:} in the absence of the Jeans scale, the mass function has a scaling symmetry with all axion star masses proportional to $1/m_a$. We show various values of the exponent $\alpha$ in the core-halo relation. \emph{Right:} including the Jeans scale induces a cut-off and breaks the exact scaling symmetry with $m_a$. We show different models for the cut-off, and different axion masses, holding $\alpha=1/3$ fixed. We use the smooth-$k$ filter as our fiducial window function (solid lines). For $m_a=10^{-11}{\rm eV}$, we also show the axion star mass functions assuming the sharp-$k$ window function (dotted) and that computed from the halo mass function fit found by~\cite{Schive:2015kza} (dashed).$ $The axion star mass function, $F_S={\rm d}n_S/{\rm d}\ln M_S$ defined by Eq.~\eqref{eqn:star-mf}, using the Sheth-Tormen halo mass function at $z=10$, assuming the core-halo mass relation, Eq.~\eqref{eqn:core-halo}. \emph{Left:} in the absence of the Jeans scale, the mass function has a scaling symmetry with all axion star masses proportional to $1/m_a$. We show various values of the exponent $\alpha$ in the core-halo relation. \emph{Right:} including the Jeans scale induces a cut-off and breaks the exact scaling symmetry with $m_a$. We show different models for the cut-off, and different axion masses, holding $\alpha=1/3$ fixed. We use the smooth-$k$ filter as our fiducial window function (solid lines). For $m_a=10^{-11}{\rm eV}$, we also show the axion star mass functions assuming the sharp-$k$ window function (dotted) and that computed from the halo mass function fit found by~\cite{Schive:2015kza} (dashed).$ Show more plots

Corresponding record in: Inspire

Rekord stworzony 2023-01-25, ostatnia modyfikacja 2024-09-13

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