Observed galaxy number counts on the lightcone up to second order: II. Derivation

Daniele Bertacca*, Roy Maartens, Chris Clarkson

*Corresponding author for this work

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We present a detailed derivation of the observed galaxy number over-density on cosmological scales up to second order in perturbation theory. We include all relativistic effects that arise from observing on the past lightcone. The derivation is in a general gauge, and applies to all dark energy models (including interacting dark energy) and to metric theories of modified gravity. The result will be important for accurate cosmological parameter estimation, including non-Gaussianity, since all projection effects need to be taken into account. It also offers the potential for new probes of General Relativity, dark energy and modified gravity. This paper accompanies Paper I which presents the key results for the concordance model in Poisson gauge.

Original languageEnglish
Article number013
Pages (from-to)013
JournalJournal of Cosmology and Astroparticle Physics
Issue number11
Early online date11 Nov 2014
Publication statusPublished - Nov 2014


  • cosmic ows
  • cosmic web
  • cosmological perturbation theory
  • gravity
  • RCUK
  • STFC
  • ST/K0090X/1


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