Constraining primordial non-Gaussianity using two galaxy surveys and CMB lensing

Mario Ballardini, William Luke Matthewson, Roy Maartens

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Next-generation galaxy surveys will be able to measure perturbations on scales beyond the equality scale. On these ultra-large scales, primordial non-Gaussianity leaves signatures that can shed light on the mechanism by which perturbations in the early Universe are generated. We perform a forecast analysis for constraining local type non-Gaussianity and its two-parameter extension with a simple scale-dependence. We combine different clustering measurements from future galaxy surveys – a 21cm intensity mapping survey and two photometric galaxy surveys – via the multi-tracer approach. Furthermore we then include CMB lensing from a CMB Stage 4 experiment in the multi-tracer, which can improve the constraints on bias parameters. We forecast σ(fNL) ≃ 0.9 (1.4) by combining SKA1, a Euclid-like (LSST-like) survey, and CMB-S4 lensing. With CMB lensing, the precision on fNL improves by up to a factor of 2, showing that a joint analysis is important. In the case with running of fNL, our results show that the combination of upcoming cosmological surveys could achieve σ(nNL) ≃ 0.12 (0.22) on the running index.
Original languageEnglish
Pages (from-to)1950-1956
Number of pages7
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
Early online date16 Aug 2019
Publication statusPublished - 1 Oct 2019


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


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