Volume 442, Number 1, October IV 2005
|Page(s)||43 - 61|
|Section||Cosmology (including clusters of galaxies)|
|Published online||30 September 2005|
Searching for galaxy clusters using the aperture mass statistics in 50 VLT fields
Institut für Astrophysik und Extraterrestrische Forschung (IAEF), Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany e-mail: email@example.com
2 Department of Physics, University “La Sapienza”, P.le A. Moro 2, 00185, Rome, Italy
3 Institut d'Astrophysique de Paris, UMR 7095 CNRS, Université Pierre & Marie Curie, 98bis boulevard Arago, 75014 Paris, France
4 Department of Physics and Astronomy, University of British Columbia, Agricultural Road 6224, Vancouver, V6T 1Z1, B.C., Canada
5 Observatoire de Paris, LERMA, 61 avenue de l'Observatoire, 75014 Paris, France
Accepted: 30 June 2005
Application of the aperture mass (Map-) statistics provides a weak lensing method for the detection of cluster-sized dark matter halos. We present a new aperture filter function and maximise the effectiveness of the Map-statistics to detect cluster-sized halos using analytical models. We then use weak lensing mock catalogues generated from ray-tracing through N-body simulations, to analyse the effect of image treatment on the expected number density of halos. Using the Map-statistics, the aperture radius is typically several arcminutes, hence the aperture often lies partly outside a data field, consequently the signal-to-noise ratio of a halo detection decreases. We study these border effects analytically and by using mock catalogues. We find that the expected number density of halos decreases by a factor of two if the size of a field is comparable to the diameter of the aperture used. We finally report on the results of a weak lensing cluster search applying the Map-statistics to 50 randomly selected fields which were observed with FORS1 at the VLT. Altogether the 50 VLT fields cover an area of 0.64 square degrees. The I-band images were taken under excellent seeing conditions (average seeing ) which results in a high number density of galaxies used for the weak lensing analysis (). In five of the VLT fields, we detect a significant Map-signal which coincides with an overdensity of the light distribution. These detections are thus excellent candidates for shear-selected clusters.
Key words: gravitational lensing / galaxies clusters: general
© ESO, 2005
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