<i>Gaia</i>GraL:<i>Gaia</i>DR2 gravitational lens systems

Ducourant, C.; Wertz, O.; Krone-Martins, A.; Teixeira, R.; Campion, J.-F. Le; Klüter, J.; Delchambre, L.; Surdej, Jean; Mignard, F.; Wambsganß, J.; Bastian, U.; Graham, M. J.; Djorgovski, S. G.; Slezak, E.

doi:10.1051/0004-6361/201833480

Cited by 26 publications

(35 citation statements)

References 95 publications

(49 reference statements)

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“…Even in this era of all-sky surveys, their discovery remains a great challenge, with barely a few hundred systems currently confirmed. A list of currently known GLs can be found in Ducourant et al (2018;hereafter Paper II).…”

Section: Introductionmentioning

confidence: 99%

Gaia GraL: Gaia DR2 gravitational lens systems

Wertz

Stern

Krone-Martins

et al. 2019

A&A

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We report the spectroscopic confirmation and modeling of the quadruply imaged quasar GRAL 113100-441959, the first gravitational lens (GL) to be discovered from a machine learning technique that only relies on the relative positions and fluxes of the observed images without considering colour informations. Follow-up spectra obtained with Keck/LRIS reveal the lensing nature of this quadruply imaged quasar with redshift z s = 1.090 ± 0.002, but show no evidence of the central lens galaxy. Using the image positions and G-band flux ratios provided by Gaia Data Release 2 as constraints, we modeled the system with a singular power-law elliptical mass distribution (SPEMD) plus external shear, to different levels of complexity. We show that relaxing the isothermal constraint of the SPEMD does not lead to statistically significant different results in terms of fitting the lensing data. We thus simplified the SPEMD to a singular isothermal ellipsoid to estimate the Einstein radius of the main lens galaxy θ E = 0. 851, the intensity and position angle of the external shear (γ, θ γ ) = (0.044, 11. • 5), and we predict the lensing galaxy position to be (θ gal,1 , θ gal,2 ) = (−0. 424, −0. 744) with respect to image A. We provide time delay predictions for pairs of images, assuming a plausible range of lens redshift values z l between 0.5 and 0.9. Finally, we examine the impact on time delays of the so-called source position transformation, a family of degeneracies existing between different mass density profiles that reproduce most of the lensing observables equally well. We show that this effect contributes significantly to the time delay error budget and cannot be ignored during the modeling. This has implications for robust cosmography applications of lensed systems. GRAL 113100-441959 is the first in a series of seven new spectroscopically confirmed GLs discovered from Gaia Data Release 2.

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Section: Introductionmentioning

confidence: 99%

Gaia GraL: Gaia DR2 gravitational lens systems

Wertz

Stern

Krone-Martins

et al. 2019

A&A

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“…Gaia will observe not only stars, but also tens of thousands of quasars, unresolved galaxies, Solar system objects, many transient and variable objects like supernovae, and finally the interstellar medium (Altavilla et al 2012;Ducourant et al 2014;Eyer et al 2014;de Bruijne et al 2015;Proft & Wambsganss 2015;Zwitter & Kos 2015;Bachchan, Hobbs, & Lindegren 2016;Tanga et al 2016). Gaia will also pose a challenge because of its data amount and complexity, pushing the astrophysical community farther into the path of big data and data mining (Gaia Collaboration 2016a).…”

Section: Introductionmentioning

confidence: 99%

Globular clusters with Gaia

Pancino

Bellazzini

Giuffrida

et al. 2017

Mon. Not. R. Astron. Soc.

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The treatment of crowded fields in Gaia data will only be a reality in a few years from now. In particular, for globular clusters, only the end-of-mission data (public in 2022-2023) will have the necessary full crowding treatment and will reach sufficient quality for the faintest stars. As a consequence, the work on the deblending and decontamination pipelines is still ongoing. We describe the present status of the pipelines for different Gaia instruments, and we model the end-of-mission crowding errors on the basis of available information. We then apply the nominal post-launch Gaia performances, appropriately worsened by the estimated crowding errors, to a set of 18 simulated globular clusters with different concentration, distance, and field contamination. We conclude that there will be 10 3 -10 4 stars with astrometric performances virtually untouched by crowding (contaminated by <1 mmag) in the majoritiy of clusters. The most limiting factor will be field crowding, not cluster crowding: the most contaminated clusters will only contain 10-100 clean stars. We also conclude that: (i) the systemic proper motions and parallaxes will be determined to 1% or better up to 15 kpc, and the nearby clusters will have radial velocities to a few km s −1 ; (ii) internal kinematics will be of unprecendented quality, cluster masses will be determined to 10% up to 15 kpc and beyond, and it will be possible to identify differences of a few km s −1 or less in the kinematics (if any) of cluster sub-populations up to 10 kpc and beyond; (iii) the brightest stars (V 17 mag) will have space-quality, wide-field photometry (mmag errors), and all Gaia photometry will have 1-3% errors on the absolute photometric calibration.

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“…For two quasars at the same redshift at such a low projected separation the first question to answer is if this is a lensed source or a physical quasar pair. An overview of more than 200 known lensed quasars can be found in Ducourant et al (2018), but unfortunately the separations are not included in the list. Currently, a handful of lensed systems are known with separation larger than 10 arcsec (Inada et al 2003(Inada et al , 2006Dahle et al 2013;Shu et al 2018) so a separation of 8.76 arcsec does not exclude that the pair under study here is a lensed system.…”

Section: Discussionmentioning

confidence: 99%

Serendipitous Discovery of a Physical Binary Quasar at z = 1.76

Altamura

Brennan

Leśniewska

et al. 2020

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Binary quasars are extremely rare objects, used to investigate clustering on very small scales at different redshifts. The cases where the two quasar components are gravitationally bound, known as physical binary quasars, can also exhibit enhanced astrophysical activity and therefore are of particular scientific interest.Here we present the serendipitous discovery of a physical pair of quasars with an angular separation of ∆θ = (8.76 ± 0.11) arcsec. The redshifts of the two quasars are consistent within the errors and measured as z = (1.76 ± 0.01). Under the motivated assumption that the pair does not arise from a single gravitationally lensed quasar, the resulting projected physical separation was estimated as (76 ± 1) kpc. For both targets we detected Si IV, C IV, C III], and Mg II emission lines.However, the two quasars show significantly different optical colours, one being among the most reddened quasars at z > 1.5 and the other with colours consistent with typical quasar colours at the same redshift. Therefore it is ruled out that the sources are a lensed system. This is our second serendipitous discovery of a pair of two quasars with different colours, having a separation 10 arcsec, which extends the very limited catalogue of known quasar pairs. We ultimately argue that the number of binary quasars may have been significantly underestimated in previous photometric surveys, due to the bias arising from paired quasars with very different colours.

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GaiaGraL:GaiaDR2 gravitational lens systems

Cited by 26 publications

References 95 publications

Gaia GraL: Gaia DR2 gravitational lens systems

Gaia GraL: Gaia DR2 gravitational lens systems

Globular clusters with Gaia

Serendipitous Discovery of a Physical Binary Quasar at z = 1.76

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