Astron. Astrophys. 341, 653-661 (1999)

6. Summary

Using the redshift and magnitude, or flux, distribution observed towards the HDF to describe background sources and Press-Schechter theory and singular isothermal sphere models to describe the foreground lensing clusters, we have calculated the expected number of lensed arcs towards galaxy clusters. We have improved previous calculations on arc statistics by including redshift information for background galaxies and accounting for the redshift evolution of foreground lensing clusters in different cosmological models. We have also accounted for the magnification bias in magnitude-limited search programs based on the HDF luminosity function. Our predicted numbers are in agreement with an extrapolation of the observed number of arcs towards a sample of bright EMSS clusters to the whole sky when in a flat universe with . Given the large systematic effects involved with both the predicted and observed number of arcs, more reliable constraints on the cosmological parameters are not currently possible.

Using the redshift and flux information for HDF radio sources, and the same lens population, we have extended the calculation to predict the expected number of lensed µJy sources towards galaxy clusters. In a cosmology with and , we predict 1500 lensed sources towards clusters with X-ray luminosities greater than , and with amplifications due to lensing greater than 2. We suggest that similar deep VLA observations may already contain lensed µJy sources and that a careful analysis may be required to establish the lensing nature of such sources.

At sub-mm wavelengths, we predict lensed sources towards clusters for same cosmology as above. We have compared our predicted numbers to the observed number of lensed sub-mm sources towards a sample of galaxy clusters. However, various biases in this observed sample and possible source contamination, do not allow us to constrain cosmological parameters based on current statistics. We have briefly studied the possibility of using the Planck surveyor and the South Pole 10-m telescope data to perform this task. A catalog of 100 lensed sources towards clusters is likely to be a useful by-product of Planck.

© European Southern Observatory (ESO) 1999

Online publication: December 16, 1998
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