A comparative study of companion galaxies around strong galaxy-galaxy lenses and non-lens galaxies: implications for dark matter halo masses

Strong galaxy-galaxy lensing is a powerful tool that, mapping the distribution of matter in the universe, is used to address specific questions in cosmology and astrophysics. More specifically, the thesis investigates and quantifies possible differences in the local environments of lens and non-lens galaxies. This environmental information is then translated, within the HOD framework, into a mass ratio between the dark matter halos hosting these galaxies.