Colloquium on 12 May 2016
The SALT Gravitational Lensing Legacy Project


Title: The SALT Gravitational Lensing Legacy Project
Speaker: Lucia Marchetti (Open University Milton Keynes (UK))
Date: Thursday, 12 May 2016
Time: 11:00 - 12:00
Venue: SAAO Auditorium


The study of strong gravitational lensing is a powerful tool for modern cosmology enabling the study of galaxy populations otherwise too faint for detailed analysis. However, its study is still in its early stages mainly because of the difficulties in identifying large, robust and unbiased samples of lensing systems, especially at high redshift.

The identification of large samples of lensing systems has been recently enabled by the advent of the Herschel Space Observatory. Because of the negative K-correction of galaxy SEDs in the sub-mm, the observed sub-mm flux of a galaxy hardly changes over the 1<z<5 range. For this reason Herschel, providing over a thousand-fold improvement in sub-mm survey mapping speed, along with the flux magnification due to lensing, allows us to detect lensing systems with background sources at much higher redshifts much more effectively than any other optical-based surveys.

In the course of its four year lifetime, Herschel has mapped approximately 1000 deg^2 of the sub-mm extragalactic sky. With our ongoing "SALT Strong Gravitational Lensing Legacy Project" we pioneer a major new strong gravitational lens selection method, combining Herschel wide-area sub-mm observations with multi-wavelength ancillary data, generating a ~500-lens homogeneous sample and obtaining SALT spectroscopy for most of them.

This is a 3-year project, started in late 2015 with a strong synergy with other observing programs with e.g. HST and ALMA.

In this seminar I will introduce the project and its scientific goals, report on its present status and first results and outline opportunities for future collaboration with South African astronomers as well as for student projects.

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