Detecting the relativistic bispectrum in 21cm intensity maps

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

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We investigate the detectability of leading-order relativistic effects in the bispectrum of future 21cm intensity mapping surveys. The relativistic signal arises from Doppler and other line-of-sight effects in redshift space. In the power spectrum of a single tracer, these effects are suppressed by a factor Script H2/k2. By contrast, in the bispectrum the relativistic signal couples to short-scale modes, leading to an imaginary contribution that scales as Script H/k, thus increasing the possibility of detection. Previous work has shown that this relativistic signal is detectable in a Stage IV Hα galaxy survey. We show that the signal is also detectable by next-generation 21cm intensity maps, but typically with a lower signal-to-noise, due to foreground and telescope beam effects.
Original languageEnglish
Article number039
Pages (from-to)1-22
Number of pages22
JournalJournal of Cosmology and Astroparticle Physics
Issue number06
Publication statusPublished - 22 Jun 2021


  • astro-ph.CO
  • UKRI
  • STFC
  • ST/S000550/1
  • ST/P000592/1


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