Probing dark energy with baryonic acoustic oscillations at high redshifts

Context. The phases and amplitudes of baryonic acoustic oscillations in the galaxy power spectrum can be used as cosmological probes to constrain different cosmological models and especially the equation of state parameter w of dark energy. Aims. It will be shown that the phases as well as the amplitudes of baryonic acoustic oscillations can be extracted out of a galaxy power spectrum, including various observational effects like growth suppression, redshift space distortions, and galaxy biasing. The phases of baryonic acoustic oscillations are used as a standard ruler for a cosmological test to constrain w over a large redshift range with a minimum of assumptions. Methods. A non-oscillating phenomenological fitting function is used to extract the oscillatory part of the galaxy power spectrum and to disentangle phase information from amplitude information. The method is tested with simulated data of the Hubble Volume Simulation to include redshift space effects, non-linear structure growth, and biasing. A cosmological test is introduced, which compares the extracted oscillations to a theoretical model template to derive constraints on the w parameter. Results. The phenomenological fitting function is found to model the various distortions of the galaxy power spectrum to the sub-percent level. The various distortions only boost the amplitude of the oscillations. The theoretical template is accurate enough to test for small deviations in the phases of the oscillations, resulting from different w values. A cosmological test, using the baryonic acoustic oscillations as a standard ruler, is able to constrain w in a robust way. These constraints are based solely on the phase of these oscillations, assuming no errors of the value at the end of the Compton drag epoch, as the standard ruler. The w constraints are expected to further improve when the full two dimensional redshift space effects and the amplitudes of the baryonic acoustic oscillations are taken into account.