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Title: Constraining the dark energy equation of state using three dimensional weak lensing
Author: Kitching, Thomas D.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2007
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The 3D cosmic shear spectral test uses the shear and redshift information from every galaxy within a survey, this work represents a refinement of the statistics presented in Heavens (2003). I treat the weakly lensed galaxies as estimators of an underlying 3D shear field. This 3D shear field can be decomposed using spherical harmonics and the spherical harmonic coefficients used to extract cosmological information. I demonstrate in particular that, in conjunction with expected results from CMB experiments, the properties of dark energy can be estimated with to high precision with large-scale, fully 3D weak lensing surveys employing the spectral test. In particular, a 5-band,10,000 square degree ground-based survey of galaxies to a median redshift of zm = 0.7 could achieve 1-σ marginal statistical errors, in combination with the constraints expected from the CMB, of Δω0 = 0.108 and Δωa = 0.099. The error on the value of ω at an intermediate pivot redshift of zp = 0.368 is constrained to Δω(zp) = 0.0175. Again, I compare and combine the 3D weak lensing constraints with the cosmological and dark energy parameters measured from planned BAO and SNIa experiments, and find that the spectral test significantly improves the marginalized errors on ω0 and ωa in combination, and provides constrains on ω(z) at a unique redshift through the lensing effect. Both of these methods have been applied to the COMBO-17 data set. The geometric test has been applied to the A901 field, which contains three clusters of galaxies. This application yields a conditional constraint of ω0 = -0.15+1.28-1/07 from only three small clusters. The spectral test has been used to analyse galaxies with redshift estimates from the CDF and S11 fields, providing a conditional constraint in the (σ8, Ωm) plane as well as a conditional constraint on ω0. The (σ8, Ωm) plane analysis constrained the relation between σ8 and Ωm to be σ8m/0.3)0.55±0.15 = 1.19 ± 0.1. The spectral tests conditional constraint on ω0 using the CDF and S11 fields is ω0 = -1.40 ± 0.55. combining the analysis from the A901 field, using the geometric tests, and the CDF and S11 fields, using the spectral test, ω0 is conditionally constrained to ω0 = -1.30+0.65-0.45. These impressive results, for such a small survey area, are shown to agree with the Fisher matrix predictions made in this thesis.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available