2025/08/01 by Zhang, Saiyang, Liu, Boyuan, Bromm, Volker · 3 citations
#Astrophysics of Galaxies (astro-ph.GA) #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences
paper · doi:10.48550/arxiv.2508.00774
We present a novel formation channel for supermassive black hole (SMBH) binaries in the early Universe, driven by primordial black holes (PBHs). Using high-resolution hydrodynamical simulations, we explore the role of massive PBHs (mBH ∼ 106 M_\odot) in catalyzing the formation of direct-collapse black holes (DCBHs), providing a natural in situ pathway for binary SMBH formation. PBHs enhance local overdensities, accelerate structure formation, and exert thermal feedback on the surrounding medium via accretion. Lyman-Werner (LW) radiation from accreting PBHs suppresses H2 cooling, shifting the dominant gas coolant to atomic hydrogen. When combined with significant baryon-dark matter streaming velocities (vbχ \gtrsim 0.8 σbχ, where σbχ is the root-mean-square streaming velocity), these effects facilitate the formation of dense, gravitationally unstable, atomically cooling gas clouds in the PBH's wake. These clouds exhibit sustained high inflow rates (Minfall \gtrsim 0.01 - 0.1 M_\odot yr-1), providing ideal conditions for DCBH formation from rapidly growing supermassive stars of ∼ 105 M_\odot at redshifts z ∼ 20 - 10. The resulting systems form SMBH binaries with initial mass ratios q ∼ O(0.1) and separations of ∼ 10 pc. Such PBH-DCBH binaries provide testable predictions for JWST and ALMA, potentially explaining select high-z sources such as the Little Red Dots (LRDs), and represent gravitational-wave sources for future missions like LISA and TianQin-bridging early-Universe black hole physics, multi-messenger astronomy, and dark matter theory.