Abstract
Context. Thanks to its spatial resolution, the ESA/Gaiaspace mission offers a unique opportunity to discover new multiply imaged quasars and to study the already known lensed systems at sub-milliarcsecond astrometric precisions.Aims. In this paper, we address the detection of the known multiply imaged quasars from theGaiaData Release 2 (DR2) and determine the astrometric and photometric properties of the individually detected images found in theGaiaDR2 catalogue.Methods. We have compiled an exhaustive list of quasar gravitational lenses from the literature to search for counterparts in theGaiaDR2. We then analysed the astrometric and photometric properties of theseGaia’s detections. To highlight the tremendous potential ofGaiaat the sub-milliarcsecond level we finally performed a simple Bayesian modelling of the well-known gravitational lens system HE0435-1223, usingGaiaDR2 and HST astrometry.Results. From 481 known multiply imaged quasars, 206 have at least one image found in theGaiaDR2. Among the 44 known quadruply imaged quasars of the list, 29 have at least one image in theGaiaDR2, 12 of which are fully detected (2MASX J01471020+4630433, HE 0435-1223, SDSS1004+4112, PG1115+080, RXJ1131-1231, 2MASS J11344050-2103230, 2MASS J13102005-1714579, B1422+231, J1606-2333, J1721+8842, WFI2033-4723, WGD2038-4008), eight have three counterparts, eight have two and one has only one. As expected, the modelling of HE0435-1223 shows that the model parameters are significantly better constrained when usingGaiaastrometry compared to HST astrometry, in particular the relative positions of the background quasar source and the centroid of the deflector. TheGaiasub-milliarcsecond astrometry also significantly reduces the parameter correlations.Conclusions. Besides providing an up-to-date list of multiply imaged quasars and their detection in theGaiaDR2, this paper shows that more complex modelling scenarios will certainly benefit fromGaiasub-milliarcsecond astrometry.
Highlights
The ESA/Gaia space mission (Gaia Collaboration 2016b) constitutes an exceptional opportunity to characterise and to discover multiply imaged quasars, this was not put forth as one of the science objectives in the mission proposal
We address the detection of the known multiply imaged quasars from the Gaia Data Release 2 (DR2) and determine the astrometric and photometric properties of the individually detected images found in the Gaia DR2 catalogue
The modelling of HE0435-1223 shows that the model parameters are significantly better constrained when using Gaia astrometry compared to Hubble Space Telescope (HST) astrometry, in particular the relative positions of the background quasar source and the centroid of the deflector
Summary
The ESA/Gaia space mission (Gaia Collaboration 2016b) constitutes an exceptional opportunity to characterise and to discover multiply imaged quasars, this was not put forth as one of the science objectives in the mission proposal. The first Gaia data release (DR1; Gaia Collaboration 2016a), besides providing the best available two-parameter astrometry (positions only) at the epoch of its publication, contained only one G mean magnitude, and it did not reach the effective angular resolution necessary to include most of the multiply imaged quasars. This happened due to data processing issues and final astrometric quality reasons (Fabricius et al 2016; Arenou et al 2017).
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