Effects of CMB temperature uncertainties on cosmological parameter estimation

TL;DR

This study assesses how uncertainties in the CMB temperature measurements impact the accuracy of cosmological parameters derived from future CMB surveys, finding the effects are generally modest and manageable.

Contribution

It quantifies the robustness of cosmological parameter estimation against CMB temperature measurement uncertainties, highlighting the minimal impact of current calibration errors.

Findings

Parameter errors are robust against a 1 mK uncertainty in CMB monopole.

Reducing temperature uncertainty by a factor of five improves precision to the percent level.

Dipole measurement uncertainties have negligible impact on parameter estimation.

Abstract

We estimate the effect of the experimental uncertainty in the measurement of the temperature of the cosmic microwave background (CMB) on the extraction of cosmological parameters from future CMB surveys. We find that even for an ideal experiment limited only by cosmic variance up to l = 2500 for both the temperature and polarisation measurements, the projected cosmological parameter errors are remarkably robust against the uncertainty of 1 mK in the FIRAS instrument's CMB temperature monopole measurement. The maximum degradation in sensitivity is 20%, for the baryon density estimate, relative to the case in which the monopole is known infinitely well. While this degradation is acceptable, we note that reducing the uncertainty in the current temperature measurement by a factor of five will bring it down to the per cent level. 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 of 0.2% from FIRAS, the sensitivity degradation is insignificant and does not exceed 10% in any parameter direction.