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arXiv · 2509.10564

Gravitational Recoil and Suppression of Super Massive Black Hole Seeds in the Early Universe

Bisweswar Sen
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Abstract

We investigate the impact of gravitational-wave (GW) recoil on the growth of supermassive black holes (SMBHs) in the early Universe. Forming 10^9 Solar Mass SMBHs by z=6 is challenging and may require hierarchical mergers of smaller seed black holes. We extend a semi-analytic seed model by explicitly incorporating GW recoil physics. Our model includes: (1) recoil velocity formulae calibrated to numerical relativity for spinning, unequal-mass BH binaries (Campanelli2007,Lousto2012); (2) assignment of spin magnitudes and orientations based on seed type (Population III remnant, stellar cluster, or direct-collapse); and (3) a retention probability scheme comparing the recoil speed to the host halo escape velocity. We find that including GW recoil reduces final SMBH masses by approximately 20-30% by z=6 and creates a population of off-nuclear (``wandering'') BHs amounting to a few percent of the total. Observable consequences include spatial offsets approximately 0.1'' and line-of-sight velocity shifts approximately 10^2-10^3 km\s in a few-percent of high-redshift quasars. All code is publicly available at https://github.com/SMALLSCALEDEV/Black-hole-Recoil-Effects

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Bisweswar Sen. 2025-09-10. Gravitational Recoil and Suppression of Super Massive Black Hole Seeds in the Early Universe. https://arxiv.org/abs/2509.10564

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