Detecting the relativistic galaxy bispectrum

Roy Maartens, Sheean Jolicoeur, Obinna Umeh, Eline M. De Weerd, Chris Clarkson, Stefano Camera

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The Fourier-space galaxy bispectrum is complex, with the imaginary part arising from leading-order relativistic corrections, due to Doppler, gravitational redshift and related line-of-sight effects in redshift space. The detection of the imaginary part of the bispectrum is potentially a smoking gun signal of relativistic contributions. We investigate whether next-generation spectroscopic surveys could make such a detection. For a Stage IV spectroscopic Hα survey similar to Euclid, we find that the cumulative signal to noise of this relativistic signature is O(10). Long-mode relativistic effects couple to short-mode Newtonian effects in the galaxy bispectrum, but not in the galaxy power spectrum. This is the basis for detectability of relativistic effects in the bispectrum of a single galaxy survey, whereas the power spectrum requires multiple galaxy surveys to detect the corresponding signal.
Original languageEnglish
Article number065
Number of pages19
JournalJournal of Cosmology and Astroparticle Physics
Issue number03
Publication statusPublished - 31 Mar 2020


  • astro-ph.CO
  • RCUK
  • STFC
  • ST/N000668/1
  • ST/K0090X/1
  • ST/P000592/1


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