talk_abstracts

Title: Extinction Curves of Lensing Galaxies (Ardis Eliasdottir)

Abstract: Dust extinction causes light from distant sources to be dimmed on its way to the observer. In cosmological studies, such as SN Ia studies, it is of great importance that the effects of dust extinction be correctly accounted for. However, although dust properties, and hence extinction, are expected to vary with redshift, not very much is known about the extinction properties of high redshift galaxies. This is because the methods traditionally used to study extinction curves are only applicable for the most nearby galaxies. Studying gravitationally lensed quasars is an emerging method of studying the dust extinction of high redshift galaxies. I will present an ESO VLT study of 10 such lensing galaxies, with redshifts up to 1. The 10 systems display varying amount and type of extinction, with the doubly imaged quasar B1152+199 showing the greatest extinction with A (V)=2.4 and R_V=2.1 for a Galactic type extinction law.

 Title: Joint Gravitational Lensing and Stellar Dynamics Analysis of Early-Type Galaxies (Matteo Barnabè)

Abstract: In this short talk I will sketch out the main features of the method we have been developing to perform a joint and fully self-consistent analysis of lens E/S0 galaxies combining information from both strong gravitational lensing and stellar dynamics. An axisymmetric gravitational potential which is function of some non-linear parameters is assumed and consistently used for both: 1. the //lensed image reconstruction// (using the non-parametric source reconstruction method described in Koopmans 2005) 2. the //dynamical modeling// (which is based on an implementation of the two-integral Schwarzschild method described by Verolme & de Zeeuw 2002). The method takes advantage of the fact that both problems are linear, and can therefore be solved in a fast and efficient non-iterative way. The most likely values for the non-linear parameters of the potential are then found with an iterative optimization scheme based on the maximization of the bayesian evidence. This approach also allows objective comparison between different sets of models. The described method is going to be applied in the next future to the sample of lens galaxies from the SLACS survey, for which full datasets are already available for about 15 systems.

 Title: Strong lensing by a galaxy member of the distant cluster Cl J0152.7-1357 (Claudio Grillo)

Abstract: I will present the gravitational lens modeling for a new example of a three-component source for which each component is quadruply imaged. The lens is a massive galaxy member of the cluster Cl J0152.7-1357 at z ~ 0.8. By taking advantage of this exceptional configuration and of the excellent angular resolution of HST/ACS, the properties of the lens can be measured accurately. I will discuss several macroscopic models for the lens galaxy. In particular, I will examine a lens model in terms of a singular isothermal sphere with external shear. The shear direction points to the cluster central mass peak and the shear modulus gives an approximate estimate of the large-scale mass, in agreement with the estimates derived from X-ray and weak lensing analyses. Then, by combining lensing analysis and spectroscopic measurements, a lower limit to the unknown redshift of the source can be found. Finally, I will show that the estimate of the projected mass inside the Einstein radius, which is a function of the source distance, can be entirely ascribed to the galaxy or partly to the galaxy and partly to the cluster, but it does not depend on the details of the adopted model.