On simple analytic models of microlensing amplification statistics

Pierre Fleury; Juan García-Bellido

doi:10.1016/j.dark.2020.100567

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arXiv · 1907.05163

On simple analytic models of microlensing amplification statistics

Pierre Fleury·Juan García-Bellido

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Abstract

Gravitational microlensing is a key probe of the nature of dark matter and its distribution on the smallest scales. For many practical purposes, confronting theory to observation requires to model the probability that a light source is highly amplified by many-lens systems. This article reviews four simple analytic models of the amplification probability distribution, based on different approximations: (i) the strongest-lens model; (ii) the multiplicative model, where the total amplification is assumed to be the product of all the lenses' individual amplifications; (iii) a hybrid version of the previous two; and (iv) an empirical fitting function. In particular, a new derivation of the multiplicative amplification distribution is proposed, thereby correcting errors in the literature. Finally, the accuracy of these models is tested against ray-shooting simulations. They all produce excellent results as long as lenses are light and rare (low optical depth); however, for larger optical depths, none of them succeeds in capturing the relevant features of the amplification distribution. This conclusion emphasizes the crucial role of lens-lens coupling at large optical depths.

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Pierre Fleury, Juan García-Bellido. 2019-07-11. On simple analytic models of microlensing amplification statistics. https://doi.org/10.1016/j.dark.2020.100567

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