Fast simulations of extragalactic microlensing

We present a new and very fast method for producing microlensing magnification maps at high optical depths. It is based on the combination of two approaches: (a) the two-dimensional Poisson solver for a deflection potential and (b) inverse polygon mapping. With our method we extremely reduce the computing time for the generation of magnification patterns and avoid the use of highly demanding computer resources. For example, the generation of a magnification map of size 2000?×?2000 pixels, covering a region of 20 Einstein radii, takes a few seconds on a state-of-the-art laptop. The method presented here will facilitate the massive production of magnification maps for extragalactic microlensing studies within the forthcoming surveys without the need for large computer clusters. The modest demand of computer power and a fast execution time allow the code developed here to be placed on a standard server and thus provide the public online access through a web-based interface.We thank Evencio Mediavilla for providing us with the IPM code for comparison purposes. We thank to the company “Datacom Soluciones Internet Burgos S.L.” (Burgos, Spain) for helping us in making the web server secure and running. We also thank an anonymous referee for his/her comments and questions that improved this paper. This research has been supported by the MINECO/AEI/FEDER-UE grant AYA2017-89815-P and University of Cantabria funds. RGM was also supported by TAILOR Grant #952215, H2020-ICT-2019-3 and DataPol UMA-CEIATECH-07 funds at the University of Málag