Constraints on the early growth of massive black holes from the PTA and JWST with L-Galaxies BH
10 affiliations
- 1Donostia International Physics Centre (DIPC)
- 2IKERBASQUE, Basque Foundation for Science
- 3Dipartimento di Fisica “G. Occhialini”, Università degli Studi di Milano-Bicocca
- 4INFN, Sezione di Milano-Bicocca
- 5Institute of Space Sciences (ICE, CSIC), Campus UAB, Carrer de Magrans
- 6Como Lake Center for AstroPhysics, University of Insubria
- 7INAF – Osservatorio Astronomico di Cagliari
- 8School of Physics and Astronomy & Institute for Gravitational Wave Astronomy, University of Birmingham
- 9University of the Basque Country UPV/EHU, Department of Theoretical Physics,
- 10Max-Planck-Institut für Astrophysik
Abstract
Recent pulsar timing array (PTA) results provide strong evidence of a stochastic gravitational wave background (sGWB), consistent with a population of merging massive black holes (MBHs) at z < 1. Meanwhile, JWST observations at z > 5 suggest a higher number density of accreting MBHs than previously estimated. Together with constraints from local MBHs and high- z quasars, these findings offer a unique opportunity to test MBH seeding and early growth models. We explored this using L-Galaxies BH , a new extension of the galaxy formation model L-Galaxies , developed to explicitly model all stages of MBH evolution, including seeding, accretion, and binary dynamics. To take advantage of both the high resolution of the MillenniumII and the large volume of the Millennium simulations, we ran L-Galaxies BH on the former and used its outputs as initial conditions for the latter, via our “grafting” method. We find that reproducing the number density of high- z active MBHs observed by JWST requires either a heavy seed formation rate that is significantly higher than that predicted by current theoretical models (≳0.01 Mpc −3 at z ∼ 10) or a widespread formation of light seeds undergoing multiple phases of super-Eddington accretion. Furthermore, matching the amplitude of the PTA sGWB signal requires nearly all galaxies with stellar masses M ∗ > 10 9 M ⊙ to host central MBHs by z ∼ 0. Given the extreme heavy seed densities required to satisfy both PTA and JWST constraints, our results favor a scenario in which MBHs originate from light seeds that grow rapidly and efficiently in the early Universe. This work demonstrates the power of combining multimessenger data with physical models to probe the origins and evolution of MBHs across cosmic time.
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BibTeX
@article{bonoli2026constraints,
title = {{Constraints on the early growth of massive black holes from the PTA and JWST with L-Galaxies BH}},
author = {Silvia Bonoli and David Izquierdo–Villalba and Daniele Spinoso and Monica Colpi and Alberto Sesana and M. Polkas and Volker Springel},
journal = {Astronomy and Astrophysics},
year = {2026},
month = jul,
doi = {10.1051/0004-6361/202557258},
url = {https://doi.org/10.1051/0004-6361/202557258},
note = {CC BY},
}
RIS
TY - JOUR
TI - Constraints on the early growth of massive black holes from the PTA and JWST with L-Galaxies BH
AU - Silvia Bonoli
AU - David Izquierdo–Villalba
AU - Daniele Spinoso
AU - Monica Colpi
AU - Alberto Sesana
AU - M. Polkas
AU - Volker Springel
PY - 2026
DA - 2026/07/31
JO - Astronomy and Astrophysics
DO - 10.1051/0004-6361/202557258
UR - https://doi.org/10.1051/0004-6361/202557258
AB - Recent pulsar timing array (PTA) results provide strong evidence of a stochastic gravitational wave background (sGWB), consistent with a population of merging massive black holes (MBHs) at z < 1. Meanwhile, JWST observations at z > 5 suggest a higher number density of accreting MBHs than previously estimated. Together with constraints from local MBHs and high- z quasars, these findings offer a unique opportunity to test MBH seeding and early growth models. We explored this using L-Galaxies BH , a new extension of the galaxy formation model L-Galaxies , developed to explicitly model all stages of MBH evolution, including seeding, accretion, and binary dynamics. To take advantage of both the high resolution of the MillenniumII and the large volume of the Millennium simulations, we ran L-Galaxies BH on the former and used its outputs as initial conditions for the latter, via our “grafting” method. We find that reproducing the number density of high- z active MBHs observed by JWST requires either a heavy seed formation rate that is significantly higher than that predicted by current theoretical models (≳0.01 Mpc −3 at z ∼ 10) or a widespread formation of light seeds undergoing multiple phases of super-Eddington accretion. Furthermore, matching the amplitude of the PTA sGWB signal requires nearly all galaxies with stellar masses M ∗ > 10 9 M ⊙ to host central MBHs by z ∼ 0. Given the extreme heavy seed densities required to satisfy both PTA and JWST constraints, our results favor a scenario in which MBHs originate from light seeds that grow rapidly and efficiently in the early Universe. This work demonstrates the power of combining multimessenger data with physical models to probe the origins and evolution of MBHs across cosmic time.
SN - 0004-6361
SN - 1432-0746
ER -