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Title: Observed galaxy number counts on the lightcone up to second order: I. Main result

Abstract

We present the galaxy number overdensity up to second order in redshift space on cosmological scales for a concordance model. The result contains all general relativistic effects up to second order that arise from observing on the past light cone, including all redshift effects, lensing distortions from convergence and shear, and contributions from velocities, Sachs-Wolfe, integrated SW and time-delay terms. This result will be important for accurate calculation of the bias on estimates of non-Gaussianity and on precision parameter estimates, introduced by nonlinear projection effects.

Authors:
;  [1];  [2]
  1. Physics Department, University of the Western Cape, Cape Town 7535 (South Africa)
  2. Centre for Astrophysics, Cosmology and Gravitation, and, Department of Mathematics and Applied Mathematics, University of Cape Town, Cape Town 7701 (South Africa)
Publication Date:
OSTI Identifier:
22375868
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Cosmology and Astroparticle Physics; Journal Volume: 2014; Journal Issue: 09; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCURACY; CONVERGENCE; GALAXIES; LIGHT CONE; NONLINEAR PROBLEMS; RED SHIFT; RELATIVISTIC RANGE; TIME DELAY

Citation Formats

Bertacca, Daniele, Maartens, Roy, and Clarkson, Chris, E-mail: daniele.bertacca@gmail.com, E-mail: roy.maartens@gmail.com, E-mail: chris.clarkson@gmail.com. Observed galaxy number counts on the lightcone up to second order: I. Main result. United States: N. p., 2014. Web. doi:10.1088/1475-7516/2014/09/037.
Bertacca, Daniele, Maartens, Roy, & Clarkson, Chris, E-mail: daniele.bertacca@gmail.com, E-mail: roy.maartens@gmail.com, E-mail: chris.clarkson@gmail.com. Observed galaxy number counts on the lightcone up to second order: I. Main result. United States. doi:10.1088/1475-7516/2014/09/037.
Bertacca, Daniele, Maartens, Roy, and Clarkson, Chris, E-mail: daniele.bertacca@gmail.com, E-mail: roy.maartens@gmail.com, E-mail: chris.clarkson@gmail.com. Mon . "Observed galaxy number counts on the lightcone up to second order: I. Main result". United States. doi:10.1088/1475-7516/2014/09/037.
@article{osti_22375868,
title = {Observed galaxy number counts on the lightcone up to second order: I. Main result},
author = {Bertacca, Daniele and Maartens, Roy and Clarkson, Chris, E-mail: daniele.bertacca@gmail.com, E-mail: roy.maartens@gmail.com, E-mail: chris.clarkson@gmail.com},
abstractNote = {We present the galaxy number overdensity up to second order in redshift space on cosmological scales for a concordance model. The result contains all general relativistic effects up to second order that arise from observing on the past light cone, including all redshift effects, lensing distortions from convergence and shear, and contributions from velocities, Sachs-Wolfe, integrated SW and time-delay terms. This result will be important for accurate calculation of the bias on estimates of non-Gaussianity and on precision parameter estimates, introduced by nonlinear projection effects.},
doi = {10.1088/1475-7516/2014/09/037},
journal = {Journal of Cosmology and Astroparticle Physics},
number = 09,
volume = 2014,
place = {United States},
year = {Mon Sep 01 00:00:00 EDT 2014},
month = {Mon Sep 01 00:00:00 EDT 2014}
}
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  • We determine the number counts to second order in cosmological perturbation theory in the Poisson gauge and allowing for anisotropic stress. The calculation is performed using an innovative approach based on the recently proposed ''geodesic light-cone'' gauge. This allows us to determine the number counts in a purely geometric way, without using Einstein's equation. The result is valid for general dark energy models and (most) modified gravity models. We then evaluate numerically some relevant contributions to the number counts bispectrum. In particular we consider the terms involving the density, redshift space distortion and lensing.
  • We review the number counts to second order concentrating on the terms which dominate on sub horizon scales. We re-derive the result for these terms and compare it with the different versions found in the literature. We generalize our derivation to higher order terms, especially the third order number counts which are needed to compute the 1-loop contribution to the power spectrum.
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  • We present an analytical model that reproduces measured galaxy number counts from surveys in the wavelength range of 500 {mu}m-2 mm. The model involves a single high-redshift galaxy population with a Schechter luminosity function that has been gravitationally lensed by galaxy clusters in the mass range 10{sup 13}-10{sup 15} M{sub sun}. This simple model reproduces both the low-flux and the high-flux end of the number counts reported by the BLAST, SCUBA, AzTEC, and South Pole Telescope (SPT) surveys. In particular, our model accounts for the most luminous galaxies detected by SPT as the result of high magnifications by galaxy clustersmore » (magnification factors of 10-30). This interpretation implies that submillimeter (submm) and millimeter surveys of this population may prove to be a useful addition to ongoing cluster detection surveys. The model also implies that the bulk of submm galaxies detected at wavelengths larger than 500 {mu}m lie at redshifts greater than 2.« less