Journal Article

Strong biases in infrared-selected gravitational lenses

Stephen Serjeant

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 424, issue 4, pages 2429-2441
Published in print August 2012 | ISSN: 0035-8711
Published online August 2012 | e-ISSN: 1365-2966 | DOI:
Strong biases in infrared-selected gravitational lenses

More Like This

Show all results sharing this subject:

  • Astronomy and Astrophysics


Show Summary Details



Bright submillimetre-selected galaxies have been found to be a rich source of strong gravitational lenses. However, strong gravitational lensing of extended sources leads inevitably to differential magnification. In this paper I quantify the effect of differential magnification on simulated far-infrared and submillimetre surveys of strong gravitational lenses, using a foreground population of Navarro–Frenk–White plus de Vaucouleurs’ density profiles, with a model source resembling the Cosmic Eyelash and quasi-stellar object J1148+5251. Some emission-line diagnostics are surprisingly unaffected by differential magnification effects: for example, the bolometric fractions of [Cii] 158 μm and CO(J = 1 − 0), often used to infer densities and ionization parameters, have typical differential magnification effects that are smaller than the measurement errors. However, the CO ladder itself is significantly affected. Far-infrared lensed galaxy surveys (e.g. at 60 μm) strongly select for high-redshift galaxies with caustics close to active galactic nuclei (AGNs), boosting the apparent bolometric contribution of AGN. The lens configuration of IRAS F10214+4724 is naturally explained in this context. Conversely, submillimetre/millimetre-wave surveys (e.g. 500–1400 μm) strongly select for caustics close to knots of star formation boosting the latter's bolometric fraction. In general, estimates of bolometric fractions from spectral energy distributions of strongly lensed infrared galaxies are so unreliable as to be useless, unless a lens mass model is available to correct for differential magnification.

Keywords: galaxies: evolution; galaxies: formation; galaxies: starburst; cosmology: observations; infrared: galaxies

Journal Article.  8683 words.  Illustrated.

Subjects: Astronomy and Astrophysics

Full text: subscription required

How to subscribe Recommend to my Librarian

Users without a subscription are not able to see the full content. Please, subscribe or login to access all content.