Weak lensing mass reconstruction of the galaxy cluster Abell 209

Context: Weak lensing applied to deep optical images of clusters of galaxies provides a powerful tool to reconstruct the distribution of the gravitating mass associated to these structures.
Aims: We use the shear signal extracted by an analysis of deep exposures of a region centered around the galaxy cluster ABCG 209, at redshift z∼ 0.2, to derive both a map of the projected mass distribution and an estimate of the total mass within a characteristic radius.
Methods: We use a series of deep archival R-band images from CFHT-12k, covering an area of 0.3 deg^2. We determine the shear of background galaxy images using a new implementation of the modified Kaiser-Squires-Broadhurst KSB+ pipeline for shear determination, which we has been tested against the "Shear TEsting Program 1 and 2'' simulations. We use mass aperture statistics to produce maps of the 2 dimensional density distribution, and parametric fits using both Navarro-Frenk-White and singular-isothermal-sphere profiles to constrain the total mass.
Results: The projected mass distribution shows a pronounced asymmetry, with an elongated structure extending from the SE to the NW. This is in general agreement with the optical distribution previously found by other authors. A similar elongation was previously detected in the X-ray emission map, and in the distribution of galaxy colours. The circular NFW mass profile fit gives a total mass of M₂₀₀ = 7.7^+4.3_-2.7× 10¹⁴ {M}_⊙ inside the virial radius r₂₀₀ = 1.8± 0.3 Mpc.
Conclusions: The weak lensing profile reinforces the evidence for an elongated structure of ABCG 209, as previously suggested by studies of the galaxy distribution and velocities.

This project has been partly supported by a Marie Curie Transfer of Knowledge Fellowship of the European Community's Sixth Framework Programme, under contract: MTKD-CT-002995 COSMOCT. Based on observations obtained at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii.