Extracting high-order cosmological information in galaxy surveys with power spectra

The reconstruction method was proposed more than a decade ago to boost the signal of baryonic acoustic oscillations measured in galaxy redshift surveys, which is one of key probes for dark energy. After moving the observed overdensities in galaxy surveys back to their initial position, the reconstructed density field is closer to a linear Gaussian field, with higher-order information moved back into the power spectrum. We find that by jointly analysing power spectra measured from the pre- and post-reconstructed galaxy samples, higher-order information beyond the 2-point power spectrum can be efficiently extracted, which generally yields an information gain upon the analysis using the pre- or post-reconstructed galaxy sample alone. This opens a window to easily use higher-order information when constraining cosmological models. Baryon Acoustic Oscillations (BAO) are formed in the early universe and can be measured galaxy redshift survey to probe dark energy, but this feature is degraded with galaxy structure evolution. The authors propose a method that simultaneously use pre- and post-reconstruction power spectra to extract higher order information for surveys to constrain cosmological models.