Bias-limited extraction of cosmological parameters

Meir Shimon*, Nissan Itzhaki, Yoel Rephaeli

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


It is known that modeling uncertainties and astrophysical foregrounds can potentially introduce appreciable bias in the deduced values of cosmological parameters. While it is commonly assumed that these uncertainties will be accounted for to a sufficient level of precision, the level of bias has not been properly quantified in most cases of interest. We show that the requirement that the bias in derived values of cosmological parameters does not surpass nominal statistical error, translates into a maximal level of overall error O(N-) on |ΔP(k)|/P(k) and |ΔCl|/Cl, where P(k), Cl, and N are the matter power spectrum, angular power spectrum, and number of (independent Fourier) modes at a given scale l or k probed by the cosmological survey, respectively. This required level has important consequences on the precision with which cosmological parameters are hoped to be determined by future surveys: in virtually all ongoing and near future surveys N typically falls in the range 106-109, implying that the required overall theoretical modeling and numerical precision is already very high. Future redshifted-21-cm observations, projected to sample ∼ 1014 modes, will require knowledge of the matter power spectrum to a fantastic 10-7 precision level. We conclude that realizing the expected potential of future cosmological surveys, which aim at detecting 106-1014 modes, sets the formidable challenge of reducing the overall level of uncertainty to 10-3-10-7.

Original languageEnglish
Article number009
JournalJournal of Cosmology and Astroparticle Physics
Issue number3
StatePublished - Mar 2013


  • cosmological parameters from CMBR
  • cosmological parameters from LSS


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