EPFL doctorate Award 2010 - Eigenbrod Alexander

"Dr. Eigenbrod used the natural phenomenon of gravitational lensing to scrutinize a distant supermassive black hole. He obtained in this way the most precise measurement, so far, of the distribution of energy around a black hole."

Astrophysical applications of gravitationally lensed quasars : from dark matter halos to the structure of quasar accretion disks.

Gravitational lensing describes how light is deflected as it passes in the vicinity of a mass distribution. The amplitude of the deflection is proportional to the mass of the deflector, called "gravitational lens". Since the discovery of the first extragalactic gravitational lens in 1979, gravitational lensing has turned from a curiosity into a powerful tool to address important astrophysical and cosmological questions.

This thesis focuses on applications related to gravitationally lensed quasars. Quasars are active galactic nuclei, where matter is heated up as it spirals down onto the central supermassive black hole. When a galaxy is located on the line of sight to a distant quasar, the foreground galaxy acts as a gravitational lens. We use this natural "magnifying glass" to probe the still mysterious inner structures of quasars achieving a spatial resolution about ten thousand times better than the capacities of current astronomical instruments.

In parallel, we have obtained spectroscopic data of this lensing galaxy with the Very Large Telescope. The modelization of the galaxy dynamics, combined with gravitational lensing, provides two independent constraints on the mass distribution and will allow to determine the quantity and distribution of dark matter in this galaxy, especially in its extended halo.

"Mention EPFL Press 2010"