Examinando por Autor "Lemon C."

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    Gravitationally lensed quasars in Gaia – IV. 150 new lenses, quasar pairs, and projected quasars
    (Oxford University Press, 2023-04-01) Lemon C.; Anguita T.; Auger-Williams M.W.; Courbin F.; Galan A.; McMahon R.; Neira F.; Oguri M.; Schechter P.; Shajib A.; Treu T.; Agnello A.; Spiniello C.
    We report the spectroscopic follow-up of 175 lensed quasar candidates selected using Gaia Data Release 2 observations following Paper III of this series. Systems include 86 confirmed lensed quasars and a further 17 likely lensed quasars based on imaging and/or similar spectra. We also confirm 11 projected quasar pairs and 11 physical quasar pairs, while 25 systems are left as unclassified quasar pairs – pairs of quasars at the same redshift, which could be either distinct quasars or potential lensed quasars. Especially interesting objects include eight quadruply imaged quasars of which two have BAL sources, an apparent triple, and a doubly lensed LoBaL quasar. The source redshifts and image separations of these new lenses range between 0.65–3.59 and 0.78–6.23 arcsec, respectively. We compare the known population of lensed quasars to an updated mock catalogue at image separations between 1 and 4 arcsec, showing a very good match at z < 1.5. At z > 1.5, only 47 per cent of the predicted number are known, with 56 per cent of these missing lenses at image separations below 1.5 arcsec. The missing higher redshift, small-separation systems will have fainter lensing galaxies, and are partially explained by the unclassified quasar pairs and likely lenses presented in this work, which require deeper imaging. Of the 11 new reported projected quasar pairs, 5 have impact parameters below 10 kpc, almost tripling the number of such systems, which can probe the innermost regions of quasar host galaxies through absorption studies. We also report four new lensed galaxies discovered through our searches, with source redshifts ranging from 0.62 to 2.79. © 2023 Oxford University Press. All rights reserved.
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    STRIDES: Automated uniform models for 30 quadruply imaged quasars
    (Oxford University Press, 2023-01) Schmidt T.; Treu T.; Birrer S.; Shajib A.J.; Lemon C.; Millon M.; Sluse D.; Agnello A.; Anguita T.; Auger-Williams M.W.; McMahon R.G.; Motta V.; Spiniello C.; Kayo I.; Courbin F.; Ertl S.; Fassnacht C.D.; Frieman J.A.; More A.; Schuldt S.; Suyu S.H.; Aguena M.; Andrade-Oliveira F.; Annis J.; Bacon D.; Bertin E.; Brooks D.; Burke D.L.; Carnero Rosell A.; Carrasco Kind M.; Carretero J.; Conselice C.; Costanzi M.; Da Costa L.N.; Pereira M.E.S.; De Vicente J.; Desai S.; Doel P.; Everett S.; Ferrero I.; Friedel D.; García-Bellido J.; Gaztanaga E.; Gruen D.; Gruendl R.A.; Gschwend J.; Gutierrez G.; Hinton S.R.; Hollowood D.L.; Honscheid K.; James D.J.; Kuehn K.; Lahav O.; Menanteau F.; Miquel R.; Palmese A.; Paz-Chinchón F.; Pieres A.; Plazas Malagón A.A.; Prat J.; Rodriguez-Monroy M.; Romer A.K.; Sanchez E.; Scarpine V.; Sevilla-Noarbe I.; Smith M.; Suchyta E.; Tarle G.; To C.; Varga T.N.
    Gravitational time delays provide a powerful one-step measurement of H0, independent of all other probes. One key ingredient in time-delay cosmography are high-accuracy lens models. Those are currently expensive to obtain, both, in terms of computing and investigator time (105-106 CPU hours and ∼0.5-1 yr, respectively). Major improvements in modelling speed are therefore necessary to exploit the large number of lenses that are forecast to be discovered over the current decade. In order to bypass this roadblock, we develop an automated modelling pipeline and apply it to a sample of 31 lens systems, observed by the Hubble Space Telescope in multiple bands. Our automated pipeline can derive models for 30/31 lenses with few hours of human time and <100 CPU hours of computing time for a typical system. For each lens, we provide measurements of key parameters and predictions of magnification as well as time delays for the multiple images. We characterize the cosmography-readiness of our models using the stability of differences in the Fermat potential (proportional to time delay) with respect to modelling choices. We find that for 10/30 lenses, our models are cosmography or nearly cosmography grade (<3 per cent and 3-5 per cent variations). For 6/30 lenses, the models are close to cosmography grade (5-10 per cent). These results utilize informative priors and will need to be confirmed by further analysis. However, they are also likely to improve by extending the pipeline modelling sequence and options. In conclusion, we show that uniform cosmography grade modelling of large strong lens samples is within reach. © 2022 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.