Developing gravitational lensing techniques to study the properties of dark matter in galaxies

• Applicant: Dr. Dominique Sluse
• Subject Area: Astrophysics and Astronomy
• Term: from 2010 to 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 185079597

My project aims at developing and applying innovative techniques to obtain a detailed mapping of the matter distribution in galaxies on kiloparsec (kpc) and sub-kiloparsec scale, using gravitational lensing as a tool. Gravitational lensing is a powerful method to derive the profile and shape of the dark matter distribution in the inner region of galaxies and to estimate the amount of substructures those galaxies are hosting (independently of whether they are luminous or not). However, to anchor the technique in solid grounds, it is necessary to understand degeneracies which exist in modeling lensing galaxies. The first part of my project aims at testing some common assumptions made in gravitational lensing, such as the use of a power-law mass distribution to model the density profile, and evaluate the impact of fundamental degeneracies in lens modeling, such as the mass-sheet degeneracy and the source-plane transformation degeneracy, on dark matter studies. The second part of the project focuses on the study of the distribution of dark matter at sub-kiloparsec scales. It will use the microlensing technique to derive the local fraction of dark matter on the line of sight towards the lensed images, and to study astrometric and photometric perturbations produced by dark matter substructures on quasar lensed images.The observational facilities which will be in operation in the next decades (e.g. the ESA mission Euclid, the European Extremely Large Telescope, the Large Synoptic Survey Telescope) will unveil and study thousands of new gravitational lenses. Hundreds of those systems will allow one to decompose the luminous and dark matter distribution of galaxies, and to derive the amount (and in some cases the mass to light ratio) of substructures in those galaxies, up to redshift one. This will be a revolution in our understanding of galaxy formation and of the properties of dark matter and of its interactions with baryons. Subtle effects and fundamental degeneracies of lens modeling need however to be fully understood to reach those goals. My project, by addressing fundamental aspects of gravitational lens modeling, will pave the ground of these upcoming researches, and provide a methodological framework to analyse those systems as well as tools to identify the most promising systems for such investigations.

• DFG Programme: Research Grants