The distortion of the images of distant galaxies by the gravity of the large-scale structure of the Universe can be a powerful tool to help us understand our Universe. By measuring this distortion, known as cosmic shear, we can constrain cosmological parameters. However, in our analyses, we make certain approximations that may no longer be valid. Anurag Deshpande, a second-year PhD student tells us about two such effects; the reduced shear approximation and magnification bias.
Cosmology is in pretty bad shape; we don’t know what makes up 95% of the Universe. Galaxies spin too fast and the expansion of the Universe is unexpectedly accelerating. Cosmologists deal with this by inferring the existence of dark matter and dark energy. These form the backbone of the Lambda Cold Dark Matter (LCDM) model. The problem is that we have no physical explanation for the existence of these two components.