Thesis PhD topic:

Gravitational Lensing as a Dark Matter and Cosmological Probe

Contact P.Rosati at ESO

Gravitational lensing is a very powerful tool to probe the distribution of dark matter on the scale of galaxies and galaxy clusters (see e.g. here for basic concepts and references). Strong and weak lensing studies of massive galaxy clusters have given us unique insights on the dark matter density profile of these systems from the core to the outskirts, providing a crucial test of cosmological structure models. In central regions of massive objects, strong lensing can significantly magnify background sources allowing the discovery and detailed spectroscopic studies of primordial galaxies which would otherwise  escape detection (gravitational telescopes).
To enable a landmark progress in this field, we have initiated a new project, CLASH (Cluster Lensing And Supernova survey with Hubble), which combines a 524-orbit HST Treasury program (PI: M.Postman) to obtain panchromatic 16-filter (ACS+WFC3) imaging of 25 massive clusters, with a VLT Large Programme (PI: P.Rosati) to conduct a VIMOS panchromatic spectroscopic survey of the 14 southern clusters from this sample.

Several thesis projects are available from the VLT-CLASH data set, which include:
i) the study of cluster mass distributions (dark matter and baryons) from a combination of dynamical, lensing and X-ray methods;
ii) the study the galaxy populations from the spectro-photometric information on thousands of cluster members over the entire cluster volume out to the surrounding field;
iii) the identification and study of primordial magnified galaxies at z>6.

For more information on the CLASH project see the Postman et al. paper and this site.

Examples of recent CLASH obervations

CLASH clusters


With current data from HST and VLT, these studies can be extended at out to redshift z~1 and beyond (see below).

Examples of strong gravitational lensing clusters
in distant clusters


RXJ0152 at z=0.83
RDCS1252 at z=1.24


RCS0224-0002 at z=0.78