• galaxy clusters
• dark matter
• Gravitational lensing

For early-type galaxies the Fundamental Plane is a scaling law equivalent to the existence of a standard rod. From a Fundamental Plane measurement of distant early-type galaxies, along the line of sight of a galaxy cluster closer to us, it is possible to detect the magnification effect on the standard rod, through which we can obtain an estimate of the projected mass density of the lens at the image positions of the distant galaxies considered.
This property can have an important appication in weak lensing-based studies of the mass profiles of galaxy clusters, because it could solve the problem of the “mass-sheet degeneracy”, which is intrinsic to this kind of diagnostics.
In this Thesis a method to break the mass-sheet degeneracy based on the joint use of weak lensing observations and Fundamental Plane measurements is developed.
The statistical properties of this mass measurement method are studied and an analytical expression for the estimated error on the determination of the mass is derived.
The method is tested with numerical simulations, which confirm the validity of the results obtained analytically.
The Thesis also addresses briefly the problem of identifying the optimal conditions on lens and source-galaxies for a significant measurement in concrete cases