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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Gaia GraL: Gaia DR2 gravitational lens systems IV. Keck/LRIS spectroscopic confirmation of GRAL 113100-441959 and model prediction of time delays

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Wertz, O. [1] ; Stern, D. [2] ; Krone-Martins, A. [3] ; Delchambre, L. [4] ; Ducourant, C. [5] ; Jorgensen, U. Grae [6] ; Dominik, M. [7] ; Burgdorf, M. [8] ; Surdej, J. [4] ; Mignard, F. [9] ; Teixeira, R. [10] ; Galluccio, L. [9] ; Klueter, J. [11] ; Djorgovski, S. G. [12] ; Graham, M. J. [12] ; Bastian, U. [11] ; Wambsganss, J. [11, 13] ; Boehm, C. [14] ; Lecampion, J-F [5] ; Slezak, E. [9]
Total Authors: 20
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[1] Univ Bonn, Argelander Inst Astron, Hugel 71, D-53121 Bonn - Germany
[2] CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 - USA
[3] Univ Lisbon, Fac Ciencias, CENTRA, Ed C8, P-1749016 Lisbon - Portugal
[4] Univ Liege, Inst Astrophys & Geophys, 19c, Allee 6 Aout, B-4000 Liege - Belgium
[5] Univ Bordeaux, Lab Astrophys Bordeaux, CNRS, B18N, Allee Geoffroy St Hilaire, F-33615 Pessac - France
[6] Kdbenhavns Univ, Niels Bohr Inst, Juliane Maries Vej 30, DK-2100 Copenhagen - Denmark
[7] Sch Phys & Astron, St Andrews, Fife - Scotland
[8] Univ Hamburg, Fac Math Informat & Nat Sci, Meteorol Inst, Dept Earth Sci, Bundesstr 55, D-20146 Hamburg - Germany
[9] Univ Cote dAzur, Observ Cote dAzur, Lab Lagrange, CNRS, Blvd Observ, CS 34229, F-06304 Nice - France
[10] Univ Sao Paulo, Inst Astron Geofis & Ciencias Atmosfer, Rua Matao 1226, Cidade Univ, BR-05508900 Sao Paulo, SP - Brazil
[11] Heidelberg Univ, Zentrum Astron, Astron Rechen Inst, Monchhofstr 12-14, D-69120 Heidelberg - Germany
[12] CALTECH, 1200 E Calif Blvd, Pasadena, CA 91125 - USA
[13] ISSI, Hallerstr 6, CH-3012 Bern - Switzerland
[14] Univ Sydney, Sch Phys, Sydney, NSW 2006 - Australia
Total Affiliations: 14
Document type: Journal article
Source: Astronomy & Astrophysics; v. 628, JUL 29 2019.
Web of Science Citations: 1

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 theta(E) = 0 `'.851, the intensity and position angle of the external shear (gamma, theta(gamma)) = (0.044, 11 degrees.5), and we predict the lensing galaxy position to be (theta(gal,1), theta(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. (AU)

FAPESP's process: 09/54006-4 - A computer cluster for the Astronomy Department of the University of São Paulo Institute of Astronomy, Geophysics and Atmospheric Sciences and for the Cruzeiro do Sul University Astrophysics Center
Grantee:Elisabete Maria de Gouveia Dal Pino
Support type: Multi-user Equipment Program