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Searching for galaxy clusters using the aperture mass statistics in 50 VLT fields

M. Hetterscheidt·T. Erben·P. Schneider·R. Maoli·L. Van Waerbeke·Y. Mellier
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Abstract

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 0.6 arcsec.) which results in a high number density of galaxies used for the weak lensing analysis (26/sq.arcmin). 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.

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M. Hetterscheidt, T. Erben, P. Schneider, R. Maoli, L. Van Waerbeke, Y. Mellier. 2005-04-28. Searching for galaxy clusters using the aperture mass statistics in 50 VLT fields. https://doi.org/10.1051/0004-6361:20053339

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