Replicate a universe
In order to study large-scale survey effects in observations, cosmologists make use of simulations. In these simulations, as many galaxies as we observe are generated, as if we create a brand new universe.
In a cosmological survey, not all galaxies are observed. This is due to various reasons, like weather, star sparkles, or survey design. Simulations have to account for the proper footprint of a survey, as well as holes that are masked out.
On the other hands, galaxies are not distant in the same way. The line-of-sight variation can correlate with the angular one.
We developped a software able to generate fast full-sky simulations. It deals with different variations properly when multiple overlapping surveys are considered together.