The multiband magnification bias for gravitational lenses

J. Stuart B. Wyithe, Joshua N. Winn, David Rusin

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


We present a generalization of the concept of magnification bias for gravitationally lensed quasars in which the quasars are selected by flux in more than one wavelength band. To illustrate the principle, we consider the case of two-band selection, in which the fluxes in the two bands are uncorrelated, perfectly correlated, or correlated with scatter. For uncorrelated fluxes, we show that the previously held result - that the bias is the product of the single-band biases - is generally false. We demonstrate some important properties of the multiband magnification bias using model luminosity functions inspired by observed correlations among X-ray, optical, infrared, and radio fluxes of quasars. In particular, the bias need not be an increasing function of each flux, and the bias can be extremely large for nonlinear correlations. The latter fact may account for the high lensing rates found in some X-ray/optical- and infrared/radio-selected samples.

Original languageEnglish (US)
Pages (from-to)58-66
Number of pages9
JournalAstrophysical Journal
Issue number1 I
StatePublished - Jan 20 2003
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • Cosmology: theory
  • Gravitational lensing


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