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Effect of clustering on primordial black hole microlensing constraints

Gorton, Matthew; Green, Anne M.

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Matthew Gorton

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Professor of Physics


Stellar microlensing observations tightly constrain compact object dark matter in the mass range (10-11-103)M ⊙. Primordial Black Holes (PBHs) form clusters, and it has been argued that these microlensing constraints are consequently weakened or evaded. For the most commonly studied PBH formation mechanism, the collapse of large gaussian curvature perturbations generated by inflation, the clusters are sufficiently extended that the PBHs within them act as individual lenses. We find that if the typical mass of the clusters is sufficiently large, ≳ 106 M ⊙, then the event duration distribution can deviate significantly from that produced by a smooth dark matter distribution, in particular at the shortest durations. As a consequence of this, the probability distribution of the number of observed events is non-Poissonian, peaking at a lower value, with an extended tail to large numbers of events. However, for PBHs formed from the collapse of large inflationary perturbations, the typical cluster is expected to contain ∼ 103 PBHs. In this case the effect of clustering is negligibly small, apart from for the most massive PBHs probed by decade-long stellar microlensing surveys (M PBH ∼ 103 M ⊙).


Gorton, M., & Green, A. M. (2022). Effect of clustering on primordial black hole microlensing constraints. Journal of Cosmology and Astroparticle Physics, 2022(08), Article 035.

Journal Article Type Article
Acceptance Date Jul 20, 2022
Online Publication Date Aug 19, 2022
Publication Date Aug 1, 2022
Deposit Date Jul 20, 2022
Publicly Available Date Aug 2, 2023
Journal Journal of Cosmology and Astroparticle Physics
Electronic ISSN 1475-7516
Peer Reviewed Peer Reviewed
Volume 2022
Issue 08
Article Number 035
Keywords paper, dark matter theory, dark matter experiments
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