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

TL;DR

This paper presents a tomographic weak lensing analysis from CFHTLenS, effectively mitigating intrinsic galaxy alignment contamination, and combines it with other cosmological data to refine constraints on cosmological parameters.

Contribution

It introduces a method to simultaneously fit cosmological and intrinsic alignment models in tomographic weak lensing analysis, improving parameter constraints.

Findings

Intrinsic alignments are galaxy-type dependent, significant for early-type galaxies.

Combined data constrains sigma_8 and Omega_m with high precision.

Intrinsic alignment contamination varies between galaxy types, affecting weak lensing results.

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 zm =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<theta<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 BOSS, and a prior on the Hubble constant from the HST distance ladder. This leads to constraints on the normalisation of the matter power spectrum sigma_8 = 0.799 +/- 0.015 and the matter density parameter Omega_m = 0.271 +/- 0.010 for a flat Lambda CDM 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 Lambda CDM 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.