2025/09/10 by B. K. Sen, Sen, Bisweswar
Physics and Astronomy · #Astrophysics of Galaxies (astro-ph.GA) #Cosmology and Gravitation Theories #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena #Instrumentation and Methods for Astrophysics (astro-ph.IM) #Relativity and Gravitational Theory #Solar and Stellar Astrophysics (astro-ph.SR)
paper · pdf · doi:10.48550/arxiv.2509.10564
openalex publication_date 2025/09/10 · openalex created_date 2025/10/09 · openalex updated_date 2026/07/28
We investigate the impact of gravitational-wave (GW) recoil on the growth of supermassive black holes (SMBHs) in the early Universe. Forming 109 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 102-103 km\s in a few-percent of high-redshift quasars. All code is publicly available at https://github.com/SMALLSCALEDEV/Black-hole-Recoil-Effects