Nonlinear modulation of the HI power spectrum on ultra-large scales. I

Obinna Umeh, Roy Maartens, Mario Santos

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Intensity mapping of the neutral hydrogen brightness temperature promises to provide a three-dimensional view of the universe on very large scales. Nonlinear effects are typically thought to alter only the small-scale power, but we show how they may bias the extraction of cosmological information contained in the power spectrum on ultra-large scales. For linear perturbations to remain valid on large scales, we need to renormalize perturbations at higher order. In the case of intensity mapping, the second-order contribution to clustering from weak lensing dominates the nonlinear contribution at high redshift. Renormalization modifies the mean brightness temperature and therefore the evolution bias. It also introduces a term that mimics white noise. These effects may influence forecasting analysis on ultra-large scales.
Original languageEnglish
Article number061
JournalJournal of Cosmology and Astroparticle Physics
Publication statusPublished - 31 Mar 2016


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


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