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26 April 2024

» arxiv » 1309.5556

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Galaxy And Mass Assembly (GAMA): improved cosmic growth measurements using multiple tracers of large-scale structure
Chris Blake ; Ivan K. Baldry ; Joss Bland-Hawthorn ; Leonidas Christodoulou ; Matthew Colless ; Christopher J. Conselice ; Simon P. Driver ; Andrew M. Hopkins ; Jochen Liske ; Jon Loveday ; Peder Norberg ; John A. Peacock ; Gregory B. Poole ; Aaron S.G. Robotham ;
Date:	22 Sep 2013
Abstract:	We present the first application of a "multiple-tracer" redshift-space distortion (RSD) analysis to an observational galaxy sample, using data from the Galaxy and Mass Assembly survey (GAMA). Our dataset is an r < 19.8 magnitude-limited sample of 178,579 galaxies covering redshift interval z < 0.5 and area 180 deg^2. We obtain improvements of 10-20% in measurements of the gravitational growth rate compared to a single-tracer analysis, deriving from the correlated sample variance imprinted in the distributions of the overlapping galaxy populations. We present new expressions for the covariances between the auto-power and cross-power spectra of galaxy samples that are valid for a general survey selection function and weighting scheme. We find no evidence for a systematic dependence of the measured growth rate on the galaxy tracer used, justifying the RSD modelling assumptions, and validate our results using mock catalogues from N-body simulations. For multiple tracers selected by galaxy colour, we measure normalized growth rates in two independent redshift bins fsigma_8(z=0.18) = 0.36 +/- 0.09 and fsigma_8(z=0.38) = 0.44 +/- 0.06, in agreement with standard GR gravity and other galaxy surveys at similar redshifts.
Source:	arXiv, 1309.5556
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