Mass and spin coevolution of black holes inspiralling through dark matter

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Main Authors: Karydas, Theophanes K., Vicente, Rodrigo, Bertone, Gianfranco
Format: Preprint
Published: 2025
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author Karydas, Theophanes K.
Vicente, Rodrigo
Bertone, Gianfranco
author_facet Karydas, Theophanes K.
Vicente, Rodrigo
Bertone, Gianfranco
contents In extreme/intermediate-mass-ratio inspirals (E/IMRIs) embedded in dark-matter (DM) spikes, the secondary black hole can accrete collisionless particles from the surrounding halo. We study how the companion's spin controls this process, and the ensuing back-reaction on the magnitude and direction of the companion's spin vector. We find that higher spin suppresses the mass accretion rate but enhances the accretion-induced torques, driving spin-down and secular alignment of the companion's spin with the orbital plane. Collisionless DM accretion generically imprints a near-universal mass-spin correlation characterized by a spin-evolution parameter $s \simeq 2.8$, much larger than is the case for typical astrophysical environments, and largely independent of the local DM density and the spike slope. The associated spin-down proceeds on astrophysically relevant timescales, thus observations of rapidly spinning IMRI companions would disfavor the presence of dense DM environments, providing constraints complementary to those arising from dynamical friction.
format Preprint
id arxiv_https___arxiv_org_abs_2510_13604
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Mass and spin coevolution of black holes inspiralling through dark matter
Karydas, Theophanes K.
Vicente, Rodrigo
Bertone, Gianfranco
General Relativity and Quantum Cosmology
Cosmology and Nongalactic Astrophysics
Astrophysics of Galaxies
High Energy Astrophysical Phenomena
High Energy Physics - Phenomenology
In extreme/intermediate-mass-ratio inspirals (E/IMRIs) embedded in dark-matter (DM) spikes, the secondary black hole can accrete collisionless particles from the surrounding halo. We study how the companion's spin controls this process, and the ensuing back-reaction on the magnitude and direction of the companion's spin vector. We find that higher spin suppresses the mass accretion rate but enhances the accretion-induced torques, driving spin-down and secular alignment of the companion's spin with the orbital plane. Collisionless DM accretion generically imprints a near-universal mass-spin correlation characterized by a spin-evolution parameter $s \simeq 2.8$, much larger than is the case for typical astrophysical environments, and largely independent of the local DM density and the spike slope. The associated spin-down proceeds on astrophysically relevant timescales, thus observations of rapidly spinning IMRI companions would disfavor the presence of dense DM environments, providing constraints complementary to those arising from dynamical friction.
title Mass and spin coevolution of black holes inspiralling through dark matter
topic General Relativity and Quantum Cosmology
Cosmology and Nongalactic Astrophysics
Astrophysics of Galaxies
High Energy Astrophysical Phenomena
High Energy Physics - Phenomenology
url https://arxiv.org/abs/2510.13604