Examinando por Autor "Napolitano, N. R."

Mostrando 1 - 2 de 2
  • No hay miniatura disponible
    Ítem
    Bright lenses are easy to find: Spectroscopic confirmation of lensed quasars in the Southern Sky
    (Monthly Notices of the Royal Astronomical Society, 2019-03-01) Spiniello, C.; Agnello, A.; Sergeyev, A. V.; Anguita, T.; Rodriguez, O.; Napolitano, N. R.; Tortora, C.
    Gravitationally lensed quasars are valuable, but extremely rare, probes of observational cosmology and extragalactic astrophysics. Progress in these fields has been limited just by the paucity of systems with good ancillary data. Here we present a first spectroscopic confirmation of lenses discovered in the Southern Sky from the DES and KiDS-DR3 footprints. We have targeted seven high-graded candidates, selected with new techniques, with NTT-EFOSC2, and confirmed five of them. We provide source spectroscopic redshifts, image separations, gri photometry, and first lens model parameters. The success rate of ∼70 percent confirms our forecasts, based on the comparison between the number of candidate doubles and quadruplets in our searches over a ≈5000 deg2 footprint and theoretical predictions.
  • Miniatura
    Ítem
    Extending the variability selection of active galactic nuclei in the W-CDF-S and SERVS/SWIRE region
    (EDP Sciences, 2020-02) Poulain, M.; Paolillo, M.; De Cicco, D.; Brandt, W.N; Bauer, , F. E.; Falocco, S.; Vagnetti, F.; Grado, A.; Ragosta, F.; Botticella, M. T.; Cappellaro, E.; Pignata, G.; Vaccar, M.; Schipani, P.; Covone, G.; Longo, G.; Napolitano, N. R.
    Context. Variability has proven to be a powerful tool to detect active galactic nuclei (AGN) in multi-epoch surveys. The new-generation facilities expected to become operational in the next few years will mark a new era in time-domain astronomy and their wide-field multi-epoch campaigns will favor extensive variability studies. Aims. We present our analysis of AGN variability in the second half of the VST survey of the Wide Chandra Deep Field South, performed in the r band and covering a 2 sq. deg area. The analysis complements a previous work, in which the first half of the area was investigated. We provide a reliable catalog of variable AGN candidates, which will be critical targets in future variability studies. Methods. We selected a sample of optically variable sources and made use of infrared data from the Spitzer mission to validate their nature by means of color-based diagnostics. Results. We obtain a sample of 782 AGN candidates among which 12 are classified as supernovae, 54 as stars, and 232 as AGN. We estimate a contamination 20% and a completeness ∼38% with respect to mid-infrared selected samples. © ESO 2020.