Internal Radiative Feedback Triggers Global Collapse and Direct-Collapse Black Hole Formation in Metal-free Atomic-Cooling Haloes
Abstract
The formation of heavy seed black holes from the collapse of supermassive stars (SMSs) is a promising pathway to the supermassive black holes (SMBHs). In the conventional direct-collapse scenario, however, SMS formation requires an extremely strong external far-ultraviolet (FUV) field to suppress H2 cooling and fragmentation. Here, we use cosmological radiation-hydrodynamic simulations to show that SMSs can form in metal-free atomic-cooling haloes even under subcritical FUV backgrounds with J21=1-102. We follow the evolution for ∼1-2 Myr after the onset of star formation, including FUV and ionizing radiation from stars formed within the halo. Star formation proceeds through a characteristic two-stage evolution. H2 cooling initially induces fragmentation and the formation of ordinary Pop III stars. Internal FUV radiation from these stars then photodissociates H2 and suppresses further fragmentation, while the surrounding warm gas reservoir contracts under self-gravity and undergoes global collapse through atomic cooling. This collapse drives inflow rates of ∼0.1-1 M⊙ yr−1 and produces rapidly accreting protostars that reach ∼2-6×104 M⊙ by the simulations end. Since rapid accretion is still ongoing, these objects are expected to grow to ∼105 M⊙ SMSs and then form direct-collapse black holes (DCBHs). The global collapse is accompanied by clustered star formation, producing a compact, top-heavy stellar system around the SMSs. The estimated DCBH abundance, nDCBH∼10−3-10−2 cMpc−3, is high enough to provide a plausible progenitor population for Little Red Dots and present-day SMBHs. Our results demonstrate that internal stellar feedback can trigger, rather than prevent, SMS formation, substantially relaxing the external FUV requirement for heavy-seed formation.
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BibTeX
@misc{kiyuna2026internal,
title = {{Internal Radiative Feedback Triggers Global Collapse and Direct-Collapse Black Hole Formation in Metal-free Atomic-Cooling Haloes}},
author = {Masaki Kiyuna and Sunmyon Chon and Kazuyuki Omukai and Raffaella Schneider},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.03877},
eprint = {2610.03877},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.03877},
}
RIS
TY - UNPB
TI - Internal Radiative Feedback Triggers Global Collapse and Direct-Collapse Black Hole Formation in Metal-free Atomic-Cooling Haloes
AU - Masaki Kiyuna
AU - Sunmyon Chon
AU - Kazuyuki Omukai
AU - Raffaella Schneider
PY - 2026
DA - 2026/10/02
PB - arXiv
DO - 10.48550/arxiv.2610.03877
UR - https://arxiv.org/abs/2610.03877
AB - The formation of heavy seed black holes from the collapse of supermassive stars (SMSs) is a promising pathway to the supermassive black holes (SMBHs). In the conventional direct-collapse scenario, however, SMS formation requires an extremely strong external far-ultraviolet (FUV) field to suppress H_2 cooling and fragmentation. Here, we use cosmological radiation-hydrodynamic simulations to show that SMSs can form in metal-free atomic-cooling haloes even under subcritical FUV backgrounds with J_21=1-10^2. We follow the evolution for ∼1-2 Myr after the onset of star formation, including FUV and ionizing radiation from stars formed within the halo. Star formation proceeds through a characteristic two-stage evolution. H_2 cooling initially induces fragmentation and the formation of ordinary Pop III stars. Internal FUV radiation from these stars then photodissociates H_2 and suppresses further fragmentation, while the surrounding warm gas reservoir contracts under self-gravity and undergoes global collapse through atomic cooling. This collapse drives inflow rates of ∼0.1-1 M_⊙ yr^−1 and produces rapidly accreting protostars that reach ∼2-6×10^4 M_⊙ by the simulations end. Since rapid accretion is still ongoing, these objects are expected to grow to ∼10^5 M_⊙ SMSs and then form direct-collapse black holes (DCBHs). The global collapse is accompanied by clustered star formation, producing a compact, top-heavy stellar system around the SMSs. The estimated DCBH abundance, n_DCBH∼10^−3-10^−2 cMpc^−3, is high enough to provide a plausible progenitor population for Little Red Dots and present-day SMBHs. Our results demonstrate that internal stellar feedback can trigger, rather than prevent, SMS formation, substantially relaxing the external FUV requirement for heavy-seed formation.
ER -