The effects of cosmic microwave background (CMB) temperature uncertainties oncosmological parameter estimation

Abstract

We estimate the effect of the experimental uncertainty in the measurement of thetemperature of the cosmic microwave background (CMB) on the extraction of cosmologicalparameters from future CMB surveys. We find that even for an ideal experiment limitedonly by cosmic variance up to for both the temperature and polarization measurements, the projected cosmologicalparameter errors are remarkably robust against the uncertainty of 1 mK in the firas CMBtemperature monopole measurement. The maximum degradation in sensitivity is20%, for the baryon density estimate, relative to the case in which the monopole is knowninfinitely well. While this degradation is acceptable, we note that reducing the uncertaintyin the current temperature measurement by a factor of five will bring it down to∼1%. We also estimate the effect of the uncertainty in the dipole temperature measurement.Assuming the overall calibration of the data to be dominated by the dipole error of0.2% from firas, the sensitivity degradation is insignificant and does not exceed 10% in anyparameter direction.