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Testing analysis algorithms

Cosmologists will use LSST to explore the structure of the Universe. The patterns of galaxies across the sky can tell us about the evolution and contents of the cosmos, the laws of gravity, and the Big Bang.Our mathematical and computational models of physics can make predictions for what patterns we will see, and we can confront those with LSST observations.

To do this we need exquisite measurements of both the brightness of galaxies, at different wavelengths, and their shapes. We use the brightness to model the distance to the galaxy, and the shapes to understand how they have been 'lensed' – distorted by the gravitational fields between us and them. With these two ingredients we can start to model the 3D structure of the 'cosmic web', the network of galaxies we can observe.

Figure 1 (taken from Debattista et al, 2017, MNRAS, 469, 1587). This plot shows the age distribution of stars in a simulation of the evolution of the stars in the Milky Way. The map is defined on a coordinate grid of (l,b), which are, respectively, Galactic Longitude and Latitude, and only the central portion of the Milky Way is plotted here. Black contours trace the age distribution (with ages indicated by the colour bar to the right of the plot), while red contours show lines of constant stellar density.

Figure 1 (taken from Debattista et al, 2017, MNRAS, 469, 1587). This plot shows the age distribution of stars in a simulation of the evolution of the stars in the Milky Way. The map is defined on a coordinate grid of (l,b), which are, respectively, Galactic Longitude and Latitude, and only the central portion of the Milky Way is plotted here. Black contours trace the age distribution (with ages indicated by the colour bar to the right of the plot), while red contours show lines of constant stellar density.

Doing this accurately enough will be an huge challenge, and to prepare for LSST we make galaxy simulations, like the one pictured above, so that we can test our algorithms and tools at the enormous data scale that the project will generate.