Galaxy And Mass Assembly (GAMA): Improved cosmic growth measurements using multiple tracers of large-scale structure

C.A. Blake, I.K. Baldry, J. Bland-Hawthorn, L. Christodoulou, M.M. Colless, C.J. Conselice, Simon Driver, A.M. Hopkins, J. Liske, J.N. Loveday, P. Norberg, J.A. Peacock, G.B. Poole, Aaron Robotham

    Research output: Contribution to journalArticlepeer-review

    133 Citations (Web of Science)


    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 (GAMA) survey. Our data set is an r <19.8 magnitude-limited sample of 178 579 galaxies covering the redshift interval z <0.5 and area 180 deg2. We obtain improvements of 10-20 per cent 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 fσ8(z = 0.18) = 0.36 ± 0.09 and fσ8(z = 0.38) = 0.44 ± 0.06, in agreement with standard GR gravity and other galaxy surveys at similar redshifts ©2013 The Authors.
    Original languageEnglish
    Pages (from-to)3089-3105
    JournalMonthly Notices of the Royal Astronomical Society
    Issue number4
    Publication statusPublished - 2013


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