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Dark Matter · Early Universe

Primordial Black Holes (PBHs)

Our research utilizes N-body simulations with the GIZMO code and semi-analytical models to investigate PBHs' impact. We find that stellar-mass PBHs (10–100 solar mass), constituting a small fraction of DM, subtly influence the formation of the universe's first stars by maintaining the standard model of star formation, while their accretion feedback shifts star formation to more massive halos. Additionally, PBHs significantly contribute to the cosmic radiation background during reionization, but do not violate existing constraints on the timing of reionization.

On the other hand, more massive PBHs with a million solar mass could seed massive halos and disrupt hierarchical structure formation by engulfing newly formed halos. In contrast to the effects of stellar-mass PBHs, our recent studies reveal that the narrative of early star formation is complicated by initial perturbations and accretion feedback from these massive PBHs at very high redshifts. Our findings also suggest that PBHs provide a viable explanation for early SMBHs like Abell2744-QSO1.

Future observations with JWST, Roman, and SKA will be critical in distinguishing PBH-driven structure formation from standard Λ-CDM scenarios.

Research Highlights

🎬 Animated SimulationClick to enlargeGIZMO cosmological hydrodynamics simulation showing gas density on the left and temperature on the right around a massive primordial black hole at t equals 14.3 Myr redshift 112.34, with PBH accretion feedback heating surrounding gas
GIZMO cosmological hydrodynamics simulation showing gas density (left) and temperature (right) around a massive primordial black hole at t = 14.3 Myr (z = 112.34). The PBH accretion feedback heats surrounding gas, influencing early star formation. (Zhang, Liu & Bromm)

Related Papers

Primordial Black Holes as Seeds for Extremely Overmassive AGN Observed by JWST

Zhang, S., Liu, B., Bromm, V., & Kühnel, F. (2025). ApJL. arXiv:2512.14066★ First Author

A direct black hole mass measurement in a Little Red Dot at the Epoch of Reionization

Juodžbalis, I., ..., Zhang, S., et al. (2025). Submitted to Nature. arXiv:2508.21748

A Novel Formation Channel for Supermassive Black Hole Binaries in the Early Universe via PBHs

Zhang, S., Liu, B., & Bromm, V. (2025). ApJ, 992(1), 136. arXiv:2508.00774★ First Author

How do Massive PBHs Impact the Formation of the First Stars and Galaxies

Zhang, S., Liu, B., Bromm, V., Jeon, J., Boylan-Kolchin, M., & Kühnel, F. (2025). ApJ, 987(2), 185. arXiv:2503.17585★ First Author

BlackTHUNDER: evidence for three massive black holes in a z~5 galaxy

Übler, H., ..., Zhang, S., et al. (2025). Submitted to A&A. arXiv:2509.21575

How do PBHs change the Halo Mass Function and Structure

Zhang, S., Bromm, V., & Liu, B. (2024). ApJ, 975(1), 139. arXiv:2405.11381★ First Author

Effects of stellar-mass PBHs on first star formation

Liu, B., Zhang, S., & Bromm, V. (2022). MNRAS, 514, 2376. arXiv:2204.06330