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

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

2005-04-28

arxiv.org/abs/astro-ph/0504635v2

A&A 442, 43-61 (2005)

Astronomy and Astrophysics

Astrophysics

23 pages, 5 tables, 24 figures, published in A&A, Sect. 3.5 and 7 are changed or altered; Fig. 11 is changed

Scientific paper

10.1051/0004-6361:20053339

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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