Cosmological measurements with general relativistic galaxy correlations

Abstract

We investigate the cosmological dependence and the constraining power of large-scale galaxy correlations, including all redshift-distortions, wide-angle, lensing and gravitational potential effects on linear scales. We analyze the cosmological information present in the lensing convergence and in the gravitational potential terms describing the so-called ``relativistic effects'', and we find that, while smaller than the information contained in intrinsic galaxy clustering, it is not negligible. We investigate how neglecting them does bias cosmological measurements performed by future spectroscopic and photometric large-scale surveys such as SKA and Euclid. We perform a Fisher analysis using the CLASS code, modified to include scale-dependent galaxy bias and redshift-dependent magnification and evolution bias. Our results show that neglecting relativistic terms, especially lensing convergence, introduces an error in the forecasted precision in measuring cosmological parameters of the order of a few tens of percent, in particular when measuring the matter content of the Universe and primordial non-Gaussianity parameters. The analysis suggests a possible substantial systematic error in cosmological parameter constraints. Therefore, we argue that radial correlations and integrated relativistic terms need to be taken into account when forecasting the constraining power of future large-scale number counts of galaxy surveys.

Additional Information

© 2016 IOP Publishing Ltd and Sissa Medialab srl. Published 3 May 2016. We thank Roy Maartens for useful contributions and for reading the manuscript, and David Alonso, Stefano Camera, Enea Di Dio and Julien Lesgourgues for helpful discussions. AR is supported by the John Templeton Foundation. Part of the research described in this paper was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. FM and RD acknowledge financial support by the Swiss National Science Foundation. During the preparation of this work DB was supported by the Deutsche Forschungsgemeinschaft through the Transregio 33, The Dark Universe, and by the South African Square Kilometre Array Project. FM and DB acknowledge the hospitality of the Department of Physics & Astronomy, Johns Hopkins University, where this work was completed.

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