Volume 523, November-December 2010
|Number of page(s)||15|
|Section||Cosmology (including clusters of galaxies)|
|Published online||11 November 2010|
The DAFT/FADA survey
I. Photometric redshifts along lines of sight to clusters in the z = [0.4, 0.9] interval⋆
LAM, OAMP, Pôle de l’Etoile Site de Château-Gombert,
38 rue Frédéric Joliot-Curie,
Marseille Cedex 13,
2 Department Physics Astronomy, Northwestern University, Evanston, IL 60208-2900, USA
3 UPMC Université Paris 06, UMR 7095, Institut d’Astrophysique de Paris, 75014 Paris, France
4 CNRS, UMR 7095, Institut d’Astrophysique de Paris, 75014 Paris, France
5 Department of Physics and Astronomy, Ohio University, 251B Clippinger Lab, Athens, OH 45701, USA
6 Fermi National Accelerator Laboratory, PO Box 500, Batavia, IL 60510, USA
7 OCA, Cassiopée, Boulevard de l’Observatoire, BP 4229, 06304 Nice Cedex 4, France
8 INAF/Osservatorio Astronomico di Trieste, via G. B. Tiepolo 11, 34143 Trieste, Italy
9 INAF - Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
10 Leiden Observatory, Leiden University, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands
11 Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, 2575 Sand Hill Road, Menlo Park, CA 94025, USA
12 Physics Department, University of California, Santa Barbara, CA 93601, USA
Accepted: 9 August 2010
Context. As a contribution to the understanding of the dark energy concept, the Dark energy American French Team (DAFT, in French FADA) has started a large project to characterize statistically high redshift galaxy clusters, infer cosmological constraints from weak lensing tomography, and understand biases relevant for constraining dark energy and cluster physics in future cluster and cosmological experiments.
Aims. The purpose of this paper is to establish the basis of reference for the photo-z determination used in all our subsequent papers, including weak lensing tomography studies.
Methods. This project is based on a sample of 91 high redshift (z ≥ 0.4), massive (≳3 × 1014 M⊙) clusters with existing HST imaging, for which we are presently performing complementary multi-wavelength imaging. This allows us in particular to estimate spectral types and determine accurate photometric redshifts for galaxies along the lines of sight to the first ten clusters for which all the required data are available down to a limit of IAB = 24./24.5 with the LePhare software. The accuracy in redshift is of the order of 0.05 for the range 0.2 ≤ z ≤ 1.5.
Results. We verified that the technique applied to obtain photometric redshifts works well by comparing our results to with previous works. In clusters, photo-z accuracy is degraded for bright absolute magnitudes and for the latest and earliest type galaxies. The photo-z accuracy also only slightly varies as a function of the spectral type for field galaxies. As a consequence, we find evidence for an environmental dependence of the photo-z accuracy, interpreted as the standard used spectral energy distributions being not very well suited to cluster galaxies. Finally, we modeled the LCDCS 0504 mass with the strong arcs detected along this line of sight.
Key words: surveys / galaxies: clusters: general / galaxies: distances and redshifts / cosmological parameters / dark energy
Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Institute and the Space Telescope European Coordinating Facility. STScI is operated by the association of Universities for Research in Astronomy, Inc. under the NASA contract NAS 5-26555. Also based on observations made with ESO Telescopes at Paranal and La Silla Observatories under programme ESO LP 166.A-0162. Also based on visiting astronomer observations, at Cerro Tololo Inter-American Observatory, National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy, under contract with the National Science Foundation.
© ESO, 2010
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