Examinando por Autor "Schechter, P.L."

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    DES meets Gaia: Discovery of strongly lensed quasars from a multiplet search
    (Oxford University Press, 2018-10) Agnello, A.; Lin, H.; Kuropatkin, N.; Buckley-Geer, E.; Anguita, T.; Schechter, P.L.; Morishita, T.; Motta, V.; Rojas, K.; Treu, T.; Amara, A.; Auger, M.W.; Courbin, F.; Fassnacht, C.D.; Frieman, J.; More, A.; Marshall, P.J.; McMahon, R.G.; Meylan, G.; Suyu, S.H.; Glazebrook, K.; Morgan, N.; Nord, B.; Abbott, T.M.C.; Abdalla, F.B.; Annis, J.; Bechtol, K.; Benoit-Lévy, K.; Bertin, E.; Bernstein, R.A.; Brooks, D.; Burke, D.L.; Carnero Rosell, A.; Carretero, J.; Cunha, C.E.; D'Andrea, C.B.; da Costa, L.N.; Desai, S.; Drlica-Wagner, A.; Eifler, T.F.; Flaugher, B.; García-Bellido, J.; Gaztanaga, E.; Gerdes, D.W.; Gruen, D.; Gruendl, R.A.; Gschwend, J.; Gutierrez, G.; Honscheid, K.; James, D.J.; Kuehn, K.; Lahav, O.; Lima, M.; Maia, M.A.G.; March, M.; Menanteau, F.; Miquel, R.; Ogando, R.L.C.; Plazas, A.A.; Sanchez, E.; Scarpine, V.; Schindler, R.; Schubnell, M.; Sevilla-Noarbe, I.; Smith, M.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Swanson, M.E.C.; Tarle, G.; Tucker, D.; Wechsler, R.
    We report the discovery, spectroscopic confirmation, and first lens models of the first, strongly lensed quasars from a combined search in WISE and Gaia-DR1 over the DES footprint. Their Einstein radii span a range between ≈2.0 arcsec and ≈0.4 arcsec. Two of these (WGD2038-4008, RA = 20:38:02.65, Dec.=-40:08:14.64; WGD2021-4115, RA = 20:21:39.45, Dec. = -41:15:57.11) also have confirmed deflector redshifts. The four-image lens WGD2038-4008, with source and deflector redshifts s = 0.777 ± 0.001 and zl = 0.230 ± 0.002, respectively, has a deflector with radius Reff ≈ 3.4 arcsec, stellar mass log(M*/M⊙) = 11.64+0.20 -0.43, and extended isophotal shape variation. Simple lens models yield Einstein radii RE = (1.30 ± 0.04) arcsec, axis ratio q = 0.75 ± 0.1 (compatible with that of the starlight) and considerable shear-ellipticity degeneracies. The two-image lens WGD2021-4115 has zs = 1.390 ± 0.001 and zl = 0.335 ± 0.002, and Einstein radius RE = (1.1 ± 0.1) arcsec, but higher-resolution imaging is needed to accurately separate the deflector and faint quasar image. Analogous lens model degeneracies hold for the other six lenses (J0146-1133, J0150-4041, J0235-2433, J0245-0556, J0259-2338, and J0508-2748) shown in this paper. © 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society.
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    Quasar lenses and pairs in the VST-ATLAS and Gaia
    (Oxford University Press, 2018-04) Agnello, A.; Schechter, P.L.; Morgan, N.D.; Treu, T.; Grillo, C.; Malesani, D.; Anguita, T.; Apostolovski, Y.; Rusu, C.E.; Motta, V.; Rojas, K.; Chehade, B.; Shanks, T.
    We report on discovery results from a quasar lens search in the ATLAS-DR3 public footprint. Spectroscopic follow-up campaigns, conducted at the 2.6 m Nordic Optical Telescope (La Palma) and 3.6mNew Technology Telescope (La Silla) in 2016, yielded seven pairs of quasars exhibiting the same lines at the same redshift and monotonic flux ratios with wavelength (hereafter NIQs, nearly identical quasar pairs). Magellan spectra of A0140-1152 (01h40m03.s0-11d52m19.s0, zs = 1.807) confirm it as a lens with deflector at zl = 0.277 and Einstein radius θE = (0.73 ± 0.02) arcsec. Follow-up imaging of the NIQ A2213-2652 (22h13m38.s4-26d52m27.s1) reveals the deflector galaxy and confirms it as a lens. We show the use of spatial resolution from the Gaia mission to select lenses and list additional systems from a WISEGaia- ATLAS search, yielding three additional lenses (02h35m27.s4-24d33m13.s2, 02h59m33s- 23d38m01.s8, 01h46m32.s9-11d33m39.s0). The overall sample consists of 11 lenses/NIQs, plus three lenses known before 2016, over the ATLAS-DR3 footprint (≈3500 deg2). Finally, we discuss future prospects for objective classification of pair/NIQ/contaminant spectra. © 2017 The Authors.
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    Serendipitous discovery of quadruply imaged quasars: Two diamonds
    (Oxford University Press, 2018-05) Lucey, J.R.; Schechter, P.L.; Smith, R.J.; Anguita, T.
    Gravitationally lensed quasars are powerful and versatile astrophysical tools, but they are challengingly rare. In particular, only ~25 well-characterized quadruple systems are known to date. To refine the target catalogue for the forthcoming Taipan Galaxy Survey, the images of a large number of sources are being visually inspected in order to identify objects that are confused by a foreground star or galaxies that have a distinct multicomponent structure. An unexpected by-product of this work has been the serendipitous discovery of about a dozen galaxies that appear to be lensing quasars, i.e. pairs or quartets of foreground stellar objects in close proximity to the target source. Here, we report two diamond-shaped systems. Follow-up spectroscopy with the IMACS instrument on the 6.5mMagellan Baade telescope confirms one of these as a z=1.975 quasar quadruply lensed by a double galaxy at z=0.293. Photometry from publicly available survey images supports the conclusion that the other system is a highly sheared quadruply imaged quasar. In starting with objects thought to be galaxies, our lens finding technique complements the conventional approach of first identifying sources with quasar-like colours and subsequently finding evidence of lensing. © 2017 The Authors.
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    The STRong lensing Insights into the Dark Energy Survey (STRIDES) 2016 follow-up campaign - I. Overview and classification of candidates selected by two techniques
    (Oxford University Press, 2018-11) Treu, T.; Agnello, A.; Baumer, M.A.; Birrer, S.; Buckley-Geer, E.J.; Courbin, F.; Kim, Y.J.; Lin, H.; Marshall, P.J.; Nord, B.; Schechter, P.L.; Sivakumar, P.R.; Abramson, L.E.; Anguita, T.; Apostolovski, Y.; Auger, M.W.; Chan, J.; Chen, G.; Collett, T.E.; Fassnacht, C.D.; Hsueh, J.-W.; Lemon, C.; McMahon, R.G.; Motta, V.; Ostrovski, F.; Rojas, K.; Rusu, C.E.; Williams, P.; Frieman, J.; Meylan, G.; Suyu, S.H.; Abbott, T.M.C.; Abdalla, F.B.; Allam, S.; Annis, J.; Avila, S.; Banerji, M.; Brooks, D.; Rosell, A.C.; Carrasco Kind, M.; Carretero, J.; Castander, F.J.; D'Andrea, C.B.; da Costa, L.N.; De Vicente, J.; Doel, P.; Eifler, T.F.; Flaugher, B.; Fosalba, P.; García-Bellido, J.; Goldstein, D.A.; Gruen, D.; Gruendl, R.A.; Gutierrez, G.; Hartley, W.G.; Hollowood, D.; Honscheid, K.; James, D.J.; Kuehn, K.; Kuropatkin, N.; Lima, M.; Maia, M.A.G.; Martini, P.; Menanteau, F.; Miquel, R.; Plazas, A.A.; Romer, A.K.; Sanchez, E.; Scarpine, V.; Schindler, R.; Schubnell, M.; Sevilla-Noarbe, I.; Smith, M.; Smith, R.C.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Swanson, M.E.C.; Tarle, G.; Thomas, D.; Tucker, D.L.; Walker, A.R.
    The primary goals of the STRong lensing Insights into the Dark Energy Survey (STRIDES) collaboration are to measure the dark energy equation of state parameter and the free streaming length of dark matter. To this aim, STRIDES is discovering strongly lensed quasars in the imaging data of the Dark Energy Survey and following them up to measure time delays, high resolution imaging, and spectroscopy sufficient to construct accurate lens models. In this paper, we first present forecasts for STRIDES. Then, we describe the STRIDES classification scheme, and give an overview of the Fall 2016 follow-up campaign. We continue by detailing the results of two selection methods, the outlier selection technique and a morphological algorithm, and presenting lens models of a system that could possibly be a lensed quasar in an unusual configuration. We conclude with the summary statistics of the Fall 2016 campaign. Including searches presented in companion papers (Anguita et al.; Ostrovski et al.), STRIDES followed up 117 targets identifying 7 new strongly lensed systems, and 7 nearly identical quasars, which could be confirmed as lenses by the detection of the lens galaxy. 76 candidates were rejected and 27 remain otherwise inconclusive, for a success rate in the range of 6-35 per cent. This rate is comparable to that of previous searches like SDSS Quasar Lens Search even though the parent data set of STRIDES is purely photometric and our selection of candidates cannot rely on spectroscopic information. © 2018 The Author(s).