Speaker: Prof. Jean Surdej
Astronomical Observatory Institute, Faculty of Physics, Adam Mickiewicz University in Poznań, Poland; Space Science, Technologies and Astrophysics Research (STAR) Institute, University of Liège, Institute of Astrophysics and Geophysics, Liège, Belgium
The formation of a gravitational mirage results from the deflection of light rays by the presence of masses interposed between a light source and an observer. The study of gravitational mirages therefore provides us with important information on the age and material content of the Universe, on the history of its constituents and on the structure of the sources that generate them. We shall first recall the basic principles underlying the formation of atmospheric and gravitationally lensed mirages. By means of an optical experiment, which can be easily reproduced at home, we will show how to simulate gravitational mirages similar to those discovered in the Cosmos. A simple optical lens model (made of plexiglass) allows to account for all the image configurations (double, quadruple, arc-shaped, Einstein’s rings, …) observed among presently known gravitational lens systems. We shall then give a detailed report on a recent systematic search for multiply imaged quasars based upon observations carried out with Gaia, a still very active astrometric space observatory of the European Space Agency. Using several realistic gravitational lens models, we shall present the numbers of multiply imaged quasars expected in the Gaia survey. Based upon the non-singular isothermal ellipsoid lens model in the presence of an external shear (nSIE+ɣ), we shall describe the technique used to identify in the second data release of Gaia (DR2) gravitational lens candidates and will finally present first observational results obtained with the Keck, VLT, NTT and Gemini telescopes. A brief presentation of the 4m International Liquid Mirror Telescope project also aimed at the detection of multiply imaged quasars will be shortly described.
Seminar language: English
Chairman: Jacek Gapiński
Theme by Themesmob