Mergers of supermassive and intermediate-mass black holes in galactic nuclei from disruptions of star clusters

Abstract

Gravitational waves (GWs) offer an unprecedented opportunity to survey the sky and detect mergers of compact objects. While intermediate-mass black holes (IMBHs) have not been detected beyond any reasonable doubt with either dynamical or accretion signatures, the GW landscape appears very promising. Mergers of an IMBH with a supermassive black hole (SMBH) will be primary sources for the planned space-based mission LISA and could be observed up to the distant Universe. SMBH-IMBH binaries can be formed as a result of the migration and merger of stellar clusters at the center of galaxies, where an SMBH lurks. We build for the first time a semi-analytical framework to model this scenario, and find that the the comoving merger rate of SMBH-IMBH binaries is $\sim 10^{-4}$ Gpc${}^{-3}$ yr${}^{-1}$ in the local Universe for a unity IMBH occupation fraction, scales linearly with it, and has a peak at $z\approx 0.5$-$2$. Our model predicts $\sim 0.1$ event yr${}^{-1}$ within redshift $z\approx 3.5$ if $10\%$ of the inspiralled star clusters hosted an IMBH, while $\sim 1$ events yr${}^{-1}$ for a unity occupation fraction. More than $90\%$ of these systems will be detectable with LISA with a signal-to-noise ratio larger than $10$, promising to potentially find a family of IMBHs.

9 pages, 5 figures, accepted by ApJ

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Cited by in corpus (11)

• The Lunar Gravitational-wave Antenna: Mission Studies and Science Case
• Growing Black Holes through Successive Mergers in Galactic Nuclei: I. Methods and First Results
• A Case for a Binary Black Hole System Revealed via Quasi-Periodic Outflows
• Constraints on the Galactic Centre environment from \textit{Gaia} hypervelocity stars III: Insights on a possible companion to Sgr A*
• Constraining the cosmic merger history of intermediate-mass black holes with gravitational wave detectors
• LISA Constraints on an Intermediate-Mass Black Hole in the Galactic Centre
• Astrophysics with the Laser Interferometer Space Antenna
• Partial Tidal Disruption Events by Intermediate-mass Black Holes in Supermassive and Intermediate-mass Black Hole Binaries
• Discovery of a Dense Association of Stars in the Vicinity of the Supermassive Black Hole Sgr A*
• Prospects for joint multiband detection of intermediate-mass black holes by LGWA and the Einstein Telescope
• The Steady State of Intermediate-Mass Black Holes Near a Supermassive Black Hole