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arXiv · 1309.5556

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
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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 f*sigma_8(z=0.18) = 0.36 +/- 0.09 and f*sigma_8(z=0.38) = 0.44 +/- 0.06, in agreement with standard GR gravity and other galaxy surveys at similar redshifts.

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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. 2013-09-22. Galaxy And Mass Assembly (GAMA): improved cosmic growth measurements using multiple tracers of large-scale structure. https://doi.org/10.1093/mnras%2Fstt1791

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