CFHTLenS tomographic weak lensing cosmological parameter constraints: Mitigating the impact of intrinsic galaxy alignments

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

Abstract

We present a finely binned tomographic weak lensing analysis of the Canada–France–Hawaii Telescope Lensing Survey (CFHTLenS) mitigating contamination to the signal from the presence of intrinsic galaxy alignments via the simultaneous fit of a cosmological model and an intrinsic alignment model. CFHTLenS spans 154 square degrees in five optical bands, with accurate shear and photometric redshifts for a galaxy sample with a median redshift of z_m = 0.70. We estimate the 21 sets of cosmic shear correlation functions associated with six redshift bins, each spanning the angular range of 1.5 < θ < 35 arcmin. We combine this CFHTLenS data with auxiliary cosmological probes: the cosmic microwave background with data from WMAP7, baryon acoustic oscillations with data from Baryon Oscillation Spectroscopic Survey and a prior on the Hubble constant from the Hubble Space Telescope distance ladder. This leads to constraints on the normalization of the matter power spectrum σ_8 = 0.799 ± 0.015 and the matter density parameter Ω_m = 0.271 ± 0.010 for a flat Λ cold dark matter (ΛCDM) cosmology. For a flat wCDM cosmology, we constrain the dark energy equation-of-state parameter w = −1.02 ± 0.09. We also provide constraints for curved ΛCDM and wCDM cosmologies. We find the intrinsic alignment contamination to be galaxy-type dependent with a significant intrinsic alignment signal found for early-type galaxies, in contrast to the late-type galaxy sample for which the intrinsic alignment signal is found to be consistent with zero.

Additional Information

© 2013 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2013 April 9. Received 2013 April 9; in original form 2012 November 15. First published online: May 9, 2013. We would like to thank Benjamin Joachimi for the verification of our non-linear intrinsic alignment model theory code in addition to many constructive comments during the preparation of this paper. We also thank the referee, in addition to Sarah Bridle and Donnacha Kirk for helpful discussions about intrinsic alignment modelling. The visualization of the Monte Carlo samples and cosmological parameter constraints makes use of code adapted from COSMOLOGUI.7 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 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. 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 members of the CFHTLenS team (LF, HHi, BR, MV) between 2007 and 2011 in addition to providing travel support and expenses for team meetings. CH, EG, FS, HHo, ES, MLB and BR acknowledge support from the European Research Council under the EC FP7 grant numbers 240185 (CH, EG, FS), 279396 (HHo, ES), 280127 (MLB) and 240672 (BR). EG also acknowledges the award of an STFC studentship. TDK acknowledges support from a Royal Society University Research Fellowship. TE is supported by the Deutsche Forschungsgemeinschaft through project ER 327/3-1 and is supported by the Transregional Collaborative Research Centre TR 33 – 'The Dark Universe'. HHi is supported by the Marie Curie IOF 252760, a CITA National Fellowship and the DFG grant Hi 1495/2-1. HHo also acknowledges support from Marie Curie IRG grant 230924 and, with ES, the Netherlands Organization for Scientific Research grant number 639.042.814. YM acknowledges support from CNRS/INSU (Institut National des Sciences de l'Univers) and the Programme National Galaxies et Cosmologie (PNCG). LVW acknowledges support from the Natural Sciences and Engineering Research Council of Canada (NSERC) and the Canadian Institute for Advanced Research (CIfAR, Cosmology and Gravity programme). MLB also acknowledges the award of an STFC Advanced Fellowship (ST/I005129/1). LF acknowledges support from NSFC grants 11103012 and 10878003, Innovation Program 12ZZ134, Chen Guang project 10CG46 of SMEC, STCSM grant 11290706600 and the Pujiang Program 12PJ1406700. MJH acknowledges support from the Natural Sciences and Engineering Research Council of Canada (NSERC). TS acknowledges support from NSF through grant AST-0444059-001, SAO through grant GO0-11147A and NWO. 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 (CH, EG, AH, MK, TK, FS) 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 the project, this paper, or both. CH and LVW co-led the CFHTLenS collaboration and TK led the CFHTLenS cosmology working group.

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Submitted - 1303.1808v1.pdf

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