Characterising the line of sight towards strongly lensed quasars

Abstract

In this Master thesis, we will study a line of sight containing a strongly lensed quasar (quasi stellar objects), galaxies and a so-called gravitational lens. After a short theoretical introduction on the concepts related to this study, we will understand what characterise a gravitational lens, how spectroscopy can help us to determine the distance of celestial bodies in the same line of sight of such system and why this last information could be useful. The main objective of this Master thesis will be to investigate techniques in order to measure the redshift of sources in the line of sight of strongly lensed quasar. As we will discuss, the lights coming from the quasar are deflected by the gravitational lens and these deflections lead to the creation of virtual images of the source. Actually, if another sufficiently massive object is present in the line of sight, one should take into account a second deflection of lights. As the deflection depends on the angular distance of the lens with respect to the source, measuring the redshift of celestial bodies in the line of sight of such system is a first step in order to characterise the line of sight of strongly lensed quasar.