Radio Galaxy Zoo Talk

very possibly lensed quasar

  • WizardHowl by WizardHowl

    The source of the radio emissions here is a quasar SDSS J110334.78+111442.9 Z_sp=1.733 with strong absorption lines in its spectrum, some in pairs. This might well be the signature of a galaxy on a line-of-sight with the QSO and a sign that the QSO itself has been lensed.

    This object seems to have been shortlisted as a potential lensing candidate in 2007MNRAS.382..412O but is not mentioned in the body of the paper. In this paper there were 3132 QSOs selected based on redshift, confidence in redhsift, brightness in the i band and separation of SDSS and 2MASS sources, of which this seems to be one. The authors then applied a colour cut (g − H > 1.15(g − r) + 2.3) to look for sources with infra-red excess (this IR excess was expected to be due to the lensing galaxy, not the lensed QSO) and from their parameters, this object just misses out: from Vizier (Catalog of SDSS-DR5/2MASS spectroscopic quasars (Ofek, 2007)) : g=18.518, r=18.223 and H=15.983, thus g-H=2.535 is less than 2.63925 and this object was not examined further.

    Is this an object to examine further? The authors in the above paper needed telescope time on some very large telescopes (Universty of Hawaii 2.2m for most of their candidates and also the 8.2m Subaru, their main candidate they then used the 10m Keck to get a spectrum) and that is hardly easy to come by. Their candidate was not a radio galaxy, though, so perhaps this might be extra science justification? Right now this is all based on a RGZ user who sees absorption lines in the spectrum shown in the SDSS DR10 interactive spectrum, so it could do with some corroboration/confirmation...

    Posted

  • WizardHowl by WizardHowl

    http://radiotalk.galaxyzoo.org/#/subjects/ARG0002phe also has a possibly lensed QSO: SDSS J103437.33+142946.0 at Z_sp=1.733. There are numerous references in NED but although it has been included in automated searches looking for lensed objects (e.g. 2012AJ....143..119I and 2007MNRAS.382..412O) it seemingly has not been classified as such. It does have an extended shape and absorption including several pairs of lines. It has g=17.709mag, r=17.626mag and H=16.291mag, giving g-H=1.418 which is less than 2.39545 and thus it would not have made the colour cut (g − H > 1.15(g − r) + 2.3) for 2007MNRAS.382..412O, as with the other example above.

    If it is a lens, the separation between images is close to or slightly beyond the limit of resolution of the SDSS survey, meaning it would not be easy to confirm. What is the scientific interest in lensed QSOs in this post-SpaceWarps world? Are there many lensed QSOs that are also radio sources?

    Posted