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Normalization of the Matter Power Spectrum via Higher Order Angular Correlations of Luminous Red Galaxies

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Ashley J. Ross1, Robert J. Brunner1,2 and Adam D. Myers1

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We present a novel technique with which to measure σ8. It relies on measuring the dependence of the second-order bias of a density field on σ8, using two separate techniques. Each technique employs area-averaged angular correlation functions (bar omegaN), one relying on the shape of bar omega2, the other relying on the amplitude of s3 (s3 = bar omega3/bar omega22). We confirm the validity of this method by testing it on a mock catalog drawn from Millennium Simulation data and finding a value of σ8 − σtrue8 = − 0.002 ± 0.062. We create a catalog of photometrically selected LRGs from SDSS DR5 and separate it into three distinct data sets by photometric redshift, with median redshifts of 0.47, 0.53, and 0.61. Measurements of c2 and σ8 are made for each data set, with the assumption of a flat geometry and WMAP3 best-fit priors on Ωm, h, and Γ. We find, with increasing redshift, that c2 = 0.09 ± 0.04, 0.09 ± 0.05, and 0.09 ± 0.03, and σ8 = 0.78 ± 0.08, 0.80 ± 0.09, and 0.80 ± 0.09. We combine these three consistent σ8 measurements to produce σ8 = 0.79 ± 0.05. Allowing the parameters Ωm, h, and Γ to vary within their WMAP3 1 σ error, we find that the best-fit value of σ8 does not change by more than 8%, and we are thus confident that our measurement is accurate to within 10%. We anticipate that future surveys, such as Pan-STARRS, DES, and LSST, will be able to employ this method in order to measure σ8 to great precision, and this will serve as an important check, complementarily, on the values determined via more established methods.

Subject headings

cosmology: observations; large-scale structure of universe


Dates

Issue 2 (2008 August 1)

Received 2007 September 20, accepted for publication 2008 April 22



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