J/A+A/657/A113ivo://CDS.VizieR/J/A+A/657/A113doi:10.26093/cds/vizier.36570113CDSLemon C.Millon M.Sluse D.Courbin F.Auger M.Chan J.Paic E.,Agnello A.2022-05-18T14:25:31Z2022-01-20T06:59:24ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frgravitational-lensingquasarsgalaxiesspectroscopyHigh-redshift binary quasars provide key insights into mergers and quasar activity, and are useful tools for probing the spatial kinematics and chemistry of galaxies along the line-of-sight. However, only three sub-10-kpc binaries have been confirmed above z=1. Gravitational lensing would provide a way to easily resolve such binaries, study them in higher resolution, and provide more sightlines, though the required alignment with a massive foreground galaxy is rare. Through image deconvolution of StanCam Nordic Optical Telescope (NOT) monitoring data, we reveal two further point sources in the known, z~2.38, quadruply lensed quasar (quad), J1721+8842. An ALFOSC/NOT long-slit spectrum shows that the brighter of these two sources is a quasar with z=2.369+/-0.007 based on the CIII] line, while the CIII] redshift of the quad is z=2.364+/-0.003. Lens modelling using point source positions rules out a single source model, favouring an isothermal lens mass profile with two quasar sources separated by ~6.0kpc (0.73") in projection. Given the resolving ability from lensing and current lensed quasar statistics, this discovery suggests a large population of undiscovered, unlensed sub-10-kpc binaries. We also analyse spectra of two images of the quad, showing narrow Ly{alpha} emission within the trough of a proximate damped Lyman-{alpha} absorber (PDLA). An apparent mismatch between the continuum and narrow line flux ratios provides a new potential tool for simultaneously studying microlensing and the quasar host galaxy. Signs of the PDLA are also seen in the second source, however a deeper spectrum is still required to confirm this. Thanks to the multiple lines-of-sight from lensing and two quasar sources, this system offers simultaneous sub-parsec and kpc-scale probes of a PDLA.2022A&A...657A.113Lhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/657/A113CatalogResearchIsServedByTAP VizieR generic servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/657/A113https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/657/A113http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/657/A113https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/657/A113https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/657/A113http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/657/A113GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapdefaultJ/A+A/657/A113/listList of fits spectrarecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNxNumber of pixels along X-axismeta.numberintNyNumber of pixels along Y-axismeta.numberintObs.dateObservation datestime.epoch;obsnullablesizeSize of FITS fileKibytephys.size;meta.fitsintFileNameName of FITS file, in subdirectory fitsmeta.id;meta.fitscharTitleTitle of the FITS filemeta.title;meta.fitschar