Quasar lenses and pairs in the VST-ATLAS and Gaia

Authors :: Claudio Grillo
Veronica Motta
Paul L. Schechter
Timo Anguita
Adriano Agnello
Cristian E. Rusu
D. Malesani
Tommaso Treu
N. D. Morgan
Yordanka Apostolovski
Tom Shanks
K. Rojas
B. Chehade
Source :: Monthly notices of the Royal Astronomical Society, 2018, Vol.475(2), pp.2086-2096 [Peer Reviewed Journal]
Publication Year :: 2017
Publisher :: Oxford University Press (OUP), 2017.
Abstract: We report on discovery results from a quasar lens search in the ATLAS public footprint, extending quasar lens searches to a regime without $u-$band or fiber-spectroscopic information, using a combination of data mining techniques on multi-band catalog magnitudes and image-cutout modelling. Spectroscopic follow-up campaigns, conducted at the 2.6m Nordic Optical Telescope (La Palma) and 3.6m New 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). The quasar redshifts range between $\approx1.2$ and $\approx 2.7;$ contaminants are typically pairs of bright blue stars, quasar-star alignments along the line of sight, and narrow-line galaxies at $0.3<br />Comment: MNRAS subm. 14/09/17. Revised version after first referee report