The 2dF QSO redshift survey - XI. The QSO power spectrum

We present a power spectrum analysis of the final 2dF Quasi-Stellar Object (QSO) Redshift Survey catalogue containing 22 652 QSOs. Utilizing the huge volume probed by the QSOs, we can accurately measure power out to scales of similar to500 h (-1) Mpc and derive new constraints, at z similar to 1.4, on the matter and baryonic contents of the Universe. Importantly, these new cosmological constraints are derived at an intermediate epoch between the cosmic microwave background observations at z similar to 1000, and local (z similar to 0) studies of large-scale structure; the average QSO redshift corresponds to a look-back time of approximately two-thirds of the age of the Universe. We find that the amplitude of clustering of the QSOs at z similar to 1.4 is similar to that of present-day galaxies. The power spectra of the QSOs at high and low redshift are compared and we find little evidence for any evolution in the amplitude. Assuming a Lambda cosmology to derive the comoving distances, r (z ), to the QSOs, the power spectrum derived can be well described by a model with shape parameter Gamma= 0.13 +/- 0.02. If an Einstein-de Sitter model r (z ) is instead assumed, a slightly higher value of Gamma= 0.16 +/- 0.03 is obtained. A comparison with the Hubble Volume Lambda cold dark matter (CDM) simulation shows very good agreement over the whole range of scales considered. A standard (Omega(m) = 1) CDM model, however, predicts a much higher value of Gamma than is observed, and it is difficult to reconcile such a model with these data. We fit CDM model power spectra (assuming scale-invariant initial fluctuations), convolved with the survey window function, and corrected for redshift space distortions, and we find that models with baryon oscillations are slightly preferred, with the baryon fraction Omega(b) /Omega(m) = 0.18 +/- 0.10. The overall shape of the power spectrum provides a strong constraint on Omega(m) h (where h is the Hubble parameter), with Omega(m) h = 0.19 +/- 0.05.