In this centenary year of Einstein's theory of gravity, this session focusses on one of its most productive practical applications: the deflection of light rays by intervening masses, and the rich variety of extragalactic science underpinned by this gravitational lensing effect.

Recently, the cluster lensing community has made exciting discoveries, such as SN Refsdal and the detection of the highest redshift galaxy known to date, in the Hubble Frontier Fields. Meanwhile galaxy-scale lens systems are being revealed in unprecedented detail, e.g. by ALMA, and are informing debates on the universality of the stellar initial mass function. New facilities and surveys including GAIA, JWST, LSST, SKA, EUCLID and E-ELT promise great leaps in lens discovery and scientific exploitation. Extragalactic strong lensing is thus a timely subject for discussion at NAM 2016.

The session will cover three broad themes:

(1) Methods for discovering strong lenses: imaging and spectroscopic searches; multi-wavelength approaches; automated search methods; citizen science projects; lensed transients.

(2) Lens science: structure and substructure of dark matter halos; the initial mass function; the build-up of mass in galaxies and clusters; constraints from time delays and transients; lens modelling algorithms.

(3) Source science: lens-assisted detection of the earliest galaxies; spatially-resolved galaxy structures at high redshift; source reconstruction methods.