Examinando por Autor "Apostolovski, Y."
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Ítem A gravitationally lensed quasar discovered in OGLE(Oxford University Press, 2018-05) Kostrzewa-Rutkowska, Z.; Kozlowski, S.; Lemon, C.; Anguita, T.; Greiner, J.; Auger, M.W.; Wyrzykowski, L.; Apostolovski, Y.; Bolmer, J.; Udalski, A.; Szymański, M.K.; Soszyński, I.; Poleski, R.; Pietrukowicz, P.; Skowron, J.; Mróz, P.; Ulaczyk, K.; Pawlak, M.We report the discovery of a new gravitationally lensed quasar (double) from the Optical Gravitational Lensing Experiment (OGLE) identified inside the ~670deg2 area encompassing the Magellanic Clouds. The source was selected as one of ~60 'red W1-W2' mid-infrared objects from WISE and having a significant amount of variability in OGLE for both two (or more) nearby sources. This is the first detection of a gravitational lens, where the discovery is made 'the other way around', meaning we first measured the time delay between the two lensed quasar images of -132 < tAB < -76 d (90 per cent CL), with the median tAB ~-102 d (in the observer frame), and where the fainter image B lags image A. The system consists of the two quasar images separated by 1.5 arcsec on the sky, with I ~20.0mag and I ~19.6mag, respectively, and a lensing galaxy that becomes detectable as I ~21.5 mag source, 1.0 arcsec from image A, after subtracting the two lensed images. Both quasar images show clear AGN broad emission lines at z=2.16 in the New Technology Telescope spectra. The spectral energy distribution (SED) fitting with the fixed source redshift provided the estimate of the lensing galaxy redshift of z ~0.9 ± 0.2 (90 per cent CL), while its type is more likely to be elliptical (the SED-inferred and lens-model stellar mass is more likely present in ellipticals) than spiral (preferred redshift by the lens model). © 2018 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society.Ítem Megaparsec-scale structure around the protocluster core SPT2349-56 at z = 4.3(Oxford University Press, 2020-05) Hill, R.; Chapman, S.; Scott, D.; Apostolovski, Y.; Aravena, M.; Béthermin, M.; Bradford, C.M.; Canning, R.E.A.; De Breuck, C.; Dong, C.; González, A.; Greve, T.R.; Hayward, C.C.; Hezaveh, Y.; Litke, K.; Malkan, M.; Marrone, D.P.; Phadke, K.; Reuter, C.; Rotermund, K.; Spilker, J.; Vieira, J.D.; Weiß, A.We present an extensive ALMA spectroscopic follow-up programme of the $z\, {=}\, 4.3$ structure SPT2349-56, one of the most actively star-forming protocluster cores known, to identify additional members using their [C ii] 158 μm and CO(4-3) lines. In addition to robustly detecting the 14 previously published galaxies in this structure, we identify a further 15 associated galaxies at $z\, {=}\, 4.3$, resolving 55$\, {\pm }\,$5 per cent of the 870 μm flux density at 0.5 arcsec resolution compared to 21 arcsec single-dish data. These galaxies are distributed into a central core containing 23 galaxies extending out to 300 kpc in diameter, and a northern extension, offset from the core by 400 kpc, containing three galaxies. We discovered three additional galaxies in a red Herschel-SPIRE source 1.5 Mpc from the main structure, suggesting the existence of many other sources at the same redshift as SPT2349-56 that are not yet detected in the limited coverage of our data. An analysis of the velocity distribution of the central galaxies indicates that this region may be virialized with a mass of (9$\pm 5)\, {\times }\, 10^{12}$ M⊠, while the two offset galaxy groups are about 30 and 60 per cent less massive and show significant velocity offsets from the central group. We calculate the [C ii] and far-infrared number counts, and find evidence for a break in the [C ii] luminosity function. We estimate the average SFR density within the region of SPT2349-56 containing single-dish emission (a proper diameter of 720 kpc), assuming spherical symmetry, to be roughly 4$\, {\times }\, 10^4$ M⊠yr-1 Mpc-3; this may be an order of magnitude greater than the most extreme examples seen in simulations. © 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society.Ítem 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.Ítem 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).Ítem The STRong lensing Insights into the dark energy survey (STRIDES) 2017/2018 follow-up campaign: Discovery of 10 lensed quasars and 10 quasar pairs(Oxford University Press, 2020) Lemon, C.; Auger, M.; Anguita, T.; McMahon, R.; Apostolovski, Y.; Chen, G.; Fassnacht, C.; Melo, A.; Motta, V.; Shajib, A.; Treu, T.; Agnello, A.; Buckley-Geer, E; Schechter, P.; Birrer, S.; Collett, T.; Courbin, F.; Rusu, C.; Abbott, T.; Allam, S.; Annis, J.; Avila, S.; Bertin, E.; Brooks, D.; Burke, D.; Carnero Rosell, A.; Carrasco Kind, M.; Carretero, J.; Costanzi, M.; Costa, L.; De Vicente, J.; Desai, S.; Eifler, T.; Flaugher, B.; Frieman, J.; Garcia-Bellido, J.; Gaztanaga, E.; Gerdes, D.; Gruen, D.; Gruendl, R.; Gschwend, J.; Gutierrez, G.; Honscheid, K.; James, D.; Kim, A.; Krause, E.; Kuehn, K.; Kuropatkin, N.; Lahav, O.; Lima, M.; Lin, H.; Maia, M.; March, M.; Marshall, J.; Menanteau, F.; Miquel, R.; Palmese, A.; Paz-Chinchon, F.; Plazas, A.; Roodman, A.; Sanchez, E.; Schubnell, M.; Serrano, S.; Smith, M.; Soares-Santos, M.; Suchyta, E.; Tarle, G.; Walker, A.We report the results of the STRong lensing Insights into the Dark Energy Survey (STRIDES) follow-up campaign of the late 2017/early 2018 season. We obtained spectra of 65 lensed quasar candidates with ESO Faint Object Spectrograph and Camera 2 on the NTT and Echellette Spectrograph and Imager onKeck, confirming 10 newlensed quasars and 10 quasar pairs. Eight lensed quasars are doubly imaged with source redshifts between 0.99 and 2.90, one is triply imaged (DESJ0345.2545, z = 1.68), and one is quadruply imaged (quad: DESJ0053.2012, z = 3.8). Singular isothermal ellipsoid models for the doubles, based on high-resolution imaging from SAMI on Southern Astrophysical Research Telescope or Near InfraRed Camera 2 on Keck, give total magnifications between 3.2 and 5.6, and Einstein radii between 0.49 and 1.97 arcsec. After spectroscopic follow-up, we extract multi-epoch grizY photometry of confirmed lensed quasars and contaminant quasar+star pairs from DES data using parametric multiband modelling, and compare variability in each system's components. By measuring the reduced χ2 associated with fitting all epochs to the samemagnitude, we find a simple cut on the less variable component that retains all confirmed lensed quasars, while removing 94 per cent of contaminant systems. Based on our spectroscopic follow-up, this variability information improves selection of lensed quasars and quasar pairs from 34-45 per cent to 51-70 per cent, with most remaining contaminants being star-forming galaxies. Using mock lensed quasar light curves we demonstrate that selection based only on variability will over-represent the quad fraction by 10 per cent over a complete DES magnitude-limited sample, explained by the magnification bias and hence lower luminosity/more variable sources in quads.