On simple analytic models of microlensing amplification statistics

Fleury, Pierre; García-Bellido, J.

doi:10.1016/j.dark.2020.100567

Cited by 12 publications

(6 citation statements)

References 65 publications

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“…In such situations, characterized by low optical depth, accounting only for the PBH that is the closest to the l.o.s. is sufficient to model the net lensing effect [41].…”

Section: Microlensing Searches For Machosmentioning

confidence: 99%

Microlensing constraints on clustered primordial black holes

Petač,

Lavalle,

Jedamzik

2022

Preprint

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The discovery of black-hole-binary mergers through their gravitational wave (GW) emission has reopened the exciting possibility that dark matter is made, at least partly, of primordial black holes (PBHs). However, this scenario is challenged by many observational probes that set bounds on the relative PBH abundance across a broad range of viable PBH masses. Among these bounds, the ones coming from microlensing surveys lead to the strongest constraints in the mass range from ∼ 10 −10 to a few M . The upper part of this range precisely corresponds to the mass window inside which the formation of PBHs should be boosted due to the QCD phase transition in the early Universe, which makes the microlensing probes particularly important. However, it has been argued that taking into account the inevitable clustering of PBH on small scales can significantly relax or entirely remove these bounds. While the impact of PBH clustering on the GW event rate has been studied in detail, its impact on the microlensing event rate has not yet been fully assessed.In this Letter, we address this issue, and show that clusters arising from isocurvature perturbations, that originating from PBHs formed from Gaussian initial curvature perturbations, do not alter the current microlensing constraints, as they are not sufficiently compact.

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“…In such situations, characterized by low optical depth, accounting only for the PBH that is the closest to the l.o.s. is sufficient to model the net lensing effect [41].…”

Section: Microlensing Searches For Machosmentioning

confidence: 99%

Microlensing constraints on clustered primordial black holes

Petač,

Lavalle,

Jedamzik

2022

Preprint

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“…In a more modern language, we may say that the calculation was made at first order in the micro-lensing optical depth τ, which coincides with the convergence κ if the density of the lenses were smoothed out; see e.g Fleury & García-Bellido (2020). …”

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confidence: 91%

Theoretical and numerical perspectives on cosmic distance averages

Breton,

Fleury

2020

Preprint

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The interpretation of cosmological observations relies on a notion of average Universe, which is usually taken as the homogeneous and isotropic Friedmann-Lemaître-Robertson-Walker (FLRW) model. However, inhomogeneities may statistically bias the observational averages with respect to FLRW, notably for distance measurements, due to a number of effects such as gravitational lensing and redshift perturbations. In this article, we review the main known theoretical results on average distance measures in cosmology, based on second-order perturbation theory, and fill some of their gaps. We then comprehensively test these theoretical predictions against ray tracing in a high-resolution dark-matter N-body simulation. This method allows us to describe the effect of small-scale inhomogeneities deep into the non-linear regime of structure formation, on light propagation up to z = 10. We find that numerical results are in remarkably good agreement with theoretical predictions, in the limit of super-sample variance. No unexpectedly large bias originates from the very small scales, whose effect is fully encoded in the non-linear power spectrum. Specifically, the directional average of the inverse amplification and the source-averaged amplification are compatible with unity; the change in area of surfaces of constant cosmic time is compatible with zero; the biases on other distance measures, which can reach ∼ 10 −3 at high redshift, are well understood. As a side product, we also confront the predictions of the recent finite-beam formalism with numerical data, and find excellent agreement.

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“…However, even for large mean magnifications where the lensing enters the complex regime associated with an intricate caustic network, the approximation by Rauch provides a simple way to capture broad behaviour of the magnification probability distributions found by numerical simulations (e.g. Fleury & García-Bellido 2020). Given the relative uncertainties associated with both FRB and GRB luminosity functions (James et al 2021;Banerjee et al 2021) particularly FRBs as their progenitor/s remain unknown, we will make use of this simple empirical model as opposed to vastly more computationally intensive numerical simulations.…”

Section: Magnification Probability Density Functionmentioning

confidence: 99%

The effect of gravitational lensing on fast transient event rates

Sammons

James

Trott

et al. 2022

Monthly Notices of the Royal Astronomical Society

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Fast cosmological transients such as fast radio bursts (FRBs) and gamma-ray bursts (GRBs) represent a class of sources more compact than any other cosmological object. As such they are sensitive to significant magnification via gravitational lensing from a class of lenses which are not well-constrained by observations today. Low-mass primordial black holes are one such candidate which may constitute a significant fraction of the Universe’s dark matter. Current observations only constrain their density in the nearby Universe, giving fast transients from cosmological distances the potential to form complementary constraints. Motivated by this, we calculate the effect that gravitational lensing from a cosmological distribution of compact objects would have on the observed rates of FRBs and GRBs. For static lensing geometries, we rule out the prospect that all FRBs are gravitationally lensed for a range of lens masses and show that lens masses greater than 10−5M⊙ can be constrained with 8000 un-localised high fluence FRBs at 1.4GHz, as might be detected by the next generation of FRB-finding telescopes.

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On simple analytic models of microlensing amplification statistics

Cited by 12 publications

References 65 publications

Microlensing constraints on clustered primordial black holes

Microlensing constraints on clustered primordial black holes

Theoretical and numerical perspectives on cosmic distance averages

The effect of gravitational lensing on fast transient event rates

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