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      Optimal constraints on the growth rate using the observed galaxy power spectrum

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          Abstract

          The large-scale structure growth index \(\gamma\) provides a consistency test of the standard cosmology and is a potential indicator of modified gravity. We investigate the constraints on \(\gamma\) from next-generation spectroscopic surveys, using the power spectrum that is observed in redshift space, i.e., the angular power spectrum. The angular power spectrum avoids the need for an Alcock-Packzynski correction. It also naturally incorporates cosmic evolution and wide-angle effects, without any approximation. We develop a redshift binning strategy that maximises the signal-to-noise on \(\gamma\) as a function of bin width. We include the cross-correlations between redshift bins, using a hybrid approximation when the total number of bins is computationally unfeasible. Neglecting cross-bin correlations degrades the constraints by a factor of \(\sim 1.5-2\). In our forecasts, we marginalise over the amplitude of primordial fluctuations and other standard cosmological parameters, including the dark energy equation of state parameter, as well as the clustering bias. Using only linear scales, we find that at low redshifts, a DESI-like survey and an SKA1 HI galaxy survey deliver similar errors of {\(\sim3-4\%\)}. This is matched by an intensity mapping survey with the SKA1 precursor MeerKAT. The high-redshift Euclid-like survey is at a similar level, while an intensity mapping survey on SKA1 gives the best error of \(\sim2\%\). Sub-percent errors are predicted for the futuristic SKA2 HI galaxy survey.

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          Author and article information

          Journal
          05 July 2019
          Article
          1907.02975
          6a306cd5-2da2-42bb-b1d5-6008df56aec9

          http://arxiv.org/licenses/nonexclusive-distrib/1.0/

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          21 pages, 6 figures, 5 tables. To be submitted to JCAP. Comments welcome
          astro-ph.CO

          Cosmology & Extragalactic astrophysics
          Cosmology & Extragalactic astrophysics

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