# Microlensing flux ratio predictions for Euclid

## TL;DR

This paper predicts quasar microlensing flux ratios for the Euclid survey using mock data, highlighting the importance of smooth matter fraction and proposing doubly lensed quasars as key systems for constraining lens properties.

## Contribution

It introduces a method to predict flux ratio distributions for large lens samples and assesses their use in constraining lens mass components without follow-up observations.

## Key findings

- Flux ratio properties depend mainly on smooth matter fraction.
- Doubly lensed quasars are most promising for constraining lens properties.
- Mock observations can recover underlying lens mass distributions.

## Abstract

Quasar microlensing flux ratios are used to unveil properties of the lenses in large collections of lensed quasars, like the ones expected to be produced by the Euclid survey. This is achieved by using the direct survey products, without any (expensive) follow-up observations or monitoring. First, the theoretical flux ratio distribution of samples of hundreds of mock quasar lenses is calculated for different Initial Mass Functions (IMFs) and Sersic radial profiles for the lens compact matter distribution. Then, mock observations are created and compared to the models to recover the underlying one. The most important factor for determining the flux ratio properties of such samples is the value of the smooth matter fraction at the location of the multiple images. Doubly lensed CASTLES-like quasars are the most promising systems to constrain the IMF and the mass components for a sample of lenses.