Baryon oscillations in galaxy and matter power-spectrum covariance matrices

We investigate large-amplitude baryon acoustic oscillations (BAOs) in off-diagonal entries of cosmological power-spectrum covariance matrices. These covariance-matrix BAOs describe the increased attenuation of power-spectrum BAOs caused by upward fluctuations in large-scale power. We derive an analytic approximation to covariance-matrix entries in the BAO regime, and check the analytical predictions using N-body simulations. These BAOs look much stronger than the BAOs in the power spectrum, but seem detectable only at about a 1 sigma level in gigaparsec-scale galaxy surveys. In estimating cosmological parameters using matter or galaxy power spectra, including the covariance-matrix BAOs can have a several per cent effect on error bar widths for some parameters directly related to the BAOs, such as the baryon fraction. Also, we find that including the numerous galaxies in small haloes in a survey can reduce error bars in these cosmological parameters more than the simple reduction in shot noise might suggest.