CFHTLenS tomographic weak lensing: quantifying accurate redshift distributions

Creators: Benjamin, Jonathan; Van Waerbeke, Ludovic; Heymans, Catherine; Kilbinger, Martin; Erben, Thomas; Hildebrandt, Hendrik; Hoekstra, Henk; Kitching, Thomas D.; Mellier, Yannick; Miller, Lance; Rowe, Barnaby; Schrabback, Tim; Simpson, Fergus; Coupon, Jean; Fu, Liping; Harnois-Déraps, Joachim; Hudson, Michael J.; Kuijken, Konrad; Semboloni, Elisabetta; Vafaei, Sanaz; Velander, Malin

Abstract

The Canada–France–Hawaii Telescope Lensing Survey (CFHTLenS) comprises deep multicolour (u^*g′r′i′z′) photometry spanning 154 deg^2, with accurate photometric redshifts and shape measurements. We demonstrate that the redshift probability distribution function summed over galaxies provides an accurate representation of the galaxy redshift distribution accounting for random and catastrophic errors for galaxies with best-fitting photometric redshifts z_p < 1.3. We present cosmological constraints using tomographic weak gravitational lensing by large-scale structure. We use two broad redshift bins 0.5 < z_p ≤ 0.85 and 0.85 < z_p ≤ 1.3 free of intrinsic alignment contamination, and measure the shear correlation function on angular scales in the range ∼1–40 arcmin. We show that the problematic redshift scaling of the shear signal, found in previous Canada–France–Hawaii Telescope Legacy Survey data analyses, does not affect the CFHTLenS data. For a flat Λ cold dark matter model and a fixed matter density Ω_m = 0.27, we find the normalization of the matter power spectrum σ_8 = 0.771 ± 0.041. When combined with cosmic microwave background data (Wilkinson Microwave Anisotropy Probe 7-year results), baryon acoustic oscillation data (BOSS) and a prior on the Hubble constant from the Hubble Space Telescope distance ladder, we find that CFHTLenS improves the precision of the fully marginalized parameter estimates by an average factor of 1.5-2. Combining our results with the above cosmological probes, we find Ω_m = 0.2762 ± 0.0074 and σ_8 = 0.802 ± 0.013.

Additional Information

© 2013 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2013 February 11. Received 2013 February 5; in original form 2012 December 11. First published online: March 8, 2013. This work is based on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada–France–Hawaii Telescope (CFHT) which is operated by the National Research Council (NRC) of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique (CNRS) of France and the University of Hawaii. This research used the facilities of the Canadian Astronomy Data Centre operated by the National Research Council of Canada with the support of the Canadian Space Agency. We thank the CFHT staff for successfully conducting the CFHTLS observations and in particular Jean-Charles Cuillandre and Eugene Magnier for the continuous improvement of the instrument calibration and the Elixir detrended data that we used. We also thank TERAPIX for the quality assessment and validation of individual exposures during the CFHTLS data acquisition period, and Emmanuel Bertin for developing some of the software used in this study. CFHTLenS data processing was made possible thanks to significant computing support from the NSERC Research Tools and Instruments grant programme, and to HPC specialist Ovidiu Toader. The early stages of the CFHTLenS project were made possible thanks to the support of the European Commissions Marie Curie Research Training Network DUEL (MRTN-CT-2006-036133) which directly supported LF, HHi, BR and MV between 2007 and 2011 in addition to providing travel support and expenses for team meetings. The N-body simulations used in this analysis were performed on the TCS supercomputer at the SciNet HPC Consortium. SciNet is funded by the Canada Foundation for Innovation under the auspices of Compute Canada, the Government of Ontario, Ontario Research Fund – Research Excellence and the University of Toronto. LVW acknowledges support from the Natural Sciences and Engineering Research Council of Canada. CH and FS acknowledge support from the European Research Council under the EC FP7 grant number 240185. TE is supported by the Deutsche Forschungsgemeinschaft through project ER 327/3-1 and the Transregional Collaborative Research Centre TR 33 – 'The Dark Universe'. HHo and ES acknowledge support from Marie Curie IRG grant 230924, the Netherlands Organization for Scientific Research (NWO) grant number 639.042.814 and from the European Research Council under the EC FP7 grant number 279396. HHi is supported by the Marie Curie IOF 252760, a CITA National Fellowship and the DFG grant Hi 1495/2-1. TDK acknowledges support from a Royal Society University Research Fellowship (NSERC) and the Canadian Institute for Advanced Research (CIfAR, Cosmology and Gravity programme). YM acknowledges support from CNRS/INSU (Institut National des Sciences de l'Univers) and the Programme National Galaxies et Cosmologie (PNCG). BR acknowledges support from the European Research Council in the form of a Starting Grant with number 24067. TS acknowledges support from NSF through grant AST-0444059-001, SAO through grant GO0-11147A and NWO. LF acknowledges support from NSFC grants 11103012 and 10878003, Innovation Programme 12ZZ134 and Chen Guang project 10CG46 of SMEC, and STCSM grant 11290706600 and Pujiang Programme 12PJ1406700. MJH acknowledges support from the Natural Sciences and Engineering Research Council of Canada (NSERC). MV acknowledges support from the Netherlands Organization for Scientific Research (NWO) and from the Beecroft Institute for Particle Astrophysics and Cosmology. Author Contributions. All authors contributed to the development and writing of this paper. The authorship list reflects the lead authors of this paper (JB, LVW, CH and MK) followed by two alphabetical groups. The first alphabetical group includes key contributors to the science analysis and interpretation in this paper, the founding core team and those whose long-term significant effort produced the final CFHTLenS data product. The second group covers members of the CFHTLenS team who made a significant contribution to either the project, this paper, or both. The CFHTLenS collaboration was co-led by CH and LVW and the CFHTLenS Cosmology Working Group was led by TK.

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