Multiply imaged quasi-stellar objects in the Gaia survey

Aims. We report a study on the statistical properties of the multiply imaged quasi-stellar objects (QSOs) to be detected within the Gaia survey. Methods. We considered two types of potential deflectors, the singular isothermal sphere (SIS) and the singular isothermal ellipsoid (SIE), to estimate the number of multiply imaged quasars as well as the normalized distributions of the redshifts of the lensed sources and of their associated deflectors. We also investigated the distribution of the lensing events as a function of their angular size and apparent magnitude. We compared the Gaia survey for multiply imaged quasars to typical ground-based surveys and to an ideal survey that would be carried out with a perfect instrument from space. Results. Of the 6 : 64 x 10(5) QSOs brighter than G = 20 to be detected by Gaia, we expect the discovery of about 2886 multiply imaged sources, 450 of which are expected to be produced by a late-type galaxy. We expect only similar to 1600 of these multiply imaged quasars to have an angular separation between their images that is large enough to be resolved from seeing-limited observations, and similar to 80 of them to have more than two lensed images.