Examinando por Autor "Motta V."

Mostrando 1 - 3 de 3
  • Miniatura
    Ítem
    Discovery of three strongly lensed quasars in the Sloan Digital Sky Survey
    (Oxford University Press, 2018-06) Williams P.R.; Agnello A.; Treu T.; Apostolovski Y.; Chen G.C.; Fassnacht C.D.; Hsueh J.W.; Lemaux B.C.; Motta V.; Oldham L.; Rojas K.; Rusu C.E.; Shajib A.J.; Wang X.; Abramson L.E.
    We present the discovery of three quasar lenses in the Sloan Digital Sky Survey, selected using two novel photometry-based selection techniques. The J0941+0518 system, with two point sources separated by 5.46 arcsec on either side of a galaxy, has source and lens redshifts 1.54 and 0.343. Images of J2257+2349 show two point sources separated by 1.67 arcsec on either side of an E/S0 galaxy. The extracted spectra show two images of the same quasar at zs = 2.10. SDSS J1640+1045 has two quasar spectra at zs = 1.70 and fits to the SDSS and Pan-STARRS images confirm the presence of a galaxy between the two point sources. We observed 56 photometrically selected lens candidates in this follow-up campaign, confirming three new lenses, re-discovering one known lens, and ruling out 36 candidates, with 16 still inconclusive. This initial campaign demonstrates the power of purely photometric selection techniques in finding lensed quasars. © 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society.
  • No hay miniatura disponible
    Ítem
    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.
  • Miniatura
    Ítem
    The STRong lensing Insights into the Dark Energy Survey (STRIDES) 2016 follow-up campaign - II. New quasar lenses from double component fitting
    (Oxford University Press, 2018-11) Anguita T.; Schechter P.L.; Kuropatkin N.; Morgan N.D.; Ostrovski F.; Abramson L.E.; Agnello A.; Apostolovski Y.; Fassnacht C.D.; Hsueh J.W.; Motta V.; Rojas K.; Rusu C.E.; Treu T.; Williams P.; Auger M.; Buckley-Geer E.; Lin H.; McMahon R.; Abbott T.M.C.; Allam S.; Annis J.; Bernstein R.A.; Bertin E.; Brooks D.; Burke D.L.; Carnero Rosell A.; Carrasco-Kind M.; Carretero J.; Cunha C.E.; D'Andrea C.B.; De Vicente J.; Depoy D.L.; Desai S.; DIehl H.T.; Doel P.; Flaugher B.; García-Bellido J.; Gerdes D.W.; Gschwend J.; Hartley W.G.; Hollowood D.L.; Honscheid K.; James D.J.; Kuehn K.; Lima M.; Maia M.A.G.; Miquel R.; Plazas A.A.; Sanchez E.; Scarpine V.; Smith M.; Soares-Santos M.; Sobreira F.; Suchyta E.; Tarle G.; Walker A.R.; Gruent, D.
    We report upon the follow-up of 34 candidate lensed quasars found in the Dark Energy Survey using NTT EFOSC, Magellan-IMACS, KECK-ESI, and SOAR-SAMI. These candidates were selected by a combination of double component fitting, morphological assessment, and colour analysis. Most systems followed up are indeed composed of at least one quasar image and 13 with two or more quasar images: two lenses, four projected binaries, and seven nearly identical quasar pairs (NIQs). The two systems confirmed as genuine gravitationally lensed quasars are one quadruple at $z$s = 1.713 and one double at $z$s = 1.515. Lens modelling of these two systems reveals that both systems require very little contribution from the environment to reproduce the image configuration. Nevertheless, small flux anomalies can be observed in one of the images of the quad. Further observations of nine inconclusive systems (including seven NIQs) will allow to confirm (or not) their gravitational lens nature. © 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society.