Magnification and evolution biases in large-scale structure surveys

Roy Maartens, José Carlos Fonseca, Stefano Camera, Sheean Jolicoeur, Jan-Albert Viljoen, Chris Clarkson

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Measurements of galaxy clustering in upcoming surveys such as those planned for the Euclid and Roman satellites, and the SKA Observatory, will be sensitive to distortions from lensing magnification and Doppler effects, beyond the standard redshift-space distortions. The amplitude of these contributions depends sensitively on magnification bias and evolution bias in the galaxy number density. Magnification bias quantifies the change in the observed number of galaxies gained or lost by lensing magnification, while evolution bias quantifies the physical change in the galaxy number density relative to the conserved case. These biases are given by derivatives of the number density, and consequently are very sensitive to the form of the luminosity function. We give a careful derivation of the magnification and evolution biases, clarifying a number of results in the literature. We then examine the biases for a variety of surveys, encompassing galaxy surveys and line intensity mapping at radio and optical/near-infrared wavelengths.
Original languageEnglish
Article number009
Number of pages27
JournalJournal of Cosmology and Astroparticle Physics
Issue number2021
Publication statusPublished - 6 Dec 2021


  • cosmological perturbation theory in GR and beyond
  • cosmological parameters from LSS
  • UKRI
  • STFC
  • ST/N000550/1
  • ST/P000592/1


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