Probing the Seed Effect of Supermassive Primordial Black Holes with Weak Gravitational Lensing
Abstract
We investigate the cosmological implications of supermassive primordial black holes (PBHs) as a component of dark matter (DM), focusing on their seed effect on large-scale structure formation. In contrast to the Poisson effect associated with the discrete distribution of PBHs, the seed effect arises because PBHs act as early gravitational seeds, accreting surrounding DM and developing dense DM spikes to form dressed PBHs. These structures enhance the matter power spectrum, particularly on small scales. We model their contribution within the halo-model framework under two prescriptions for DM accretion: an optimistic scenario (Case 1) and a conservative scenario (Case 2), which predict different modifications to the 1-halo term. We constrain the PBH abundance using weak-lensing measurements from the Dark Energy Survey Year 3 (DES Y3), performing a Markov Chain Monte Carlo analysis to derive upper limits on the PBH fraction fPBH, as a function of the PBH mass MPBH. We find that weak lensing places competitive constraints on supermassive PBHs, with the upper limits on fPBH becoming progressively stronger toward higher PBH masses. Case 1, which predicts more efficient DM accretion and hence a larger enhancement of the matter power spectrum, yields stronger constraints than Case 2; in particular, it excludes fPBH≳10−4 for MPBH≳1010 M⊙. We further forecast the sensitivity of the Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST) using mock weak-lensing data and find that the constraints could improve by approximately two orders of magnitude. Our results establish weak gravitational lensing as a sensitive probe of the seed effect of supermassive PBHs and demonstrate its potential to complement other cosmological and astrophysical searches.
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BibTeX
@misc{zu2026probing,
title = {{Probing the Seed Effect of Supermassive Primordial Black Holes with Weak Gravitational Lensing}},
author = {Lei Zu and Kazunori Kohri},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2611.07574},
eprint = {2611.07574},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2611.07574},
}
RIS
TY - UNPB
TI - Probing the Seed Effect of Supermassive Primordial Black Holes with Weak Gravitational Lensing
AU - Lei Zu
AU - Kazunori Kohri
PY - 2026
DA - 2026/11/05
PB - arXiv
DO - 10.48550/arxiv.2611.07574
UR - https://arxiv.org/abs/2611.07574
AB - We investigate the cosmological implications of supermassive primordial black holes (PBHs) as a component of dark matter (DM), focusing on their seed effect on large-scale structure formation. In contrast to the Poisson effect associated with the discrete distribution of PBHs, the seed effect arises because PBHs act as early gravitational seeds, accreting surrounding DM and developing dense DM spikes to form dressed PBHs. These structures enhance the matter power spectrum, particularly on small scales. We model their contribution within the halo-model framework under two prescriptions for DM accretion: an optimistic scenario (Case 1) and a conservative scenario (Case 2), which predict different modifications to the 1-halo term. We constrain the PBH abundance using weak-lensing measurements from the Dark Energy Survey Year 3 (DES Y3), performing a Markov Chain Monte Carlo analysis to derive upper limits on the PBH fraction f_PBH, as a function of the PBH mass M_PBH. We find that weak lensing places competitive constraints on supermassive PBHs, with the upper limits on f_PBH becoming progressively stronger toward higher PBH masses. Case 1, which predicts more efficient DM accretion and hence a larger enhancement of the matter power spectrum, yields stronger constraints than Case 2; in particular, it excludes f_PBH≳10^−4 for M_PBH≳10^10 M_⊙. We further forecast the sensitivity of the Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST) using mock weak-lensing data and find that the constraints could improve by approximately two orders of magnitude. Our results establish weak gravitational lensing as a sensitive probe of the seed effect of supermassive PBHs and demonstrate its potential to complement other cosmological and astrophysical searches.
ER -