The 2dF QSO Redshift Survey - IV. The QSO Power Spectrum from the 10k Catalogue

We present a power spectrum analysis of the 10K catalogue from the 2dF QSO Redshift Survey. Although the Survey currently has a patchy angular selection func- tion, we use the Virgo Consortium's Hubble Volume simulation to demonstrate that we are able to make a useful first measurement of the power spectrum over more than a decade in scale. We compare the redshift-space power spectra of QSOs to those measured for galaxies and Abell clusters at low redshift and find that they show similar shapes in their overlap range, 50-150h 1 Mpc, with PQSO(k) / k 1.4 . The amplitude of the QSO power spectrum at z � 1.4 is almost comparable to that of galaxies at the present day if m=0.3 and �=0.7 (thecosmology), and a factor of � 3 lower if m=1 (the EdS cosmology) is assumed. The amplitude of the QSO power spectrum is a factor of � 10 lower than that measured for Abell clusters at the present day. At larger scales, the QSO power spectra continue to rise robustly to � 400 h 1 Mpc, implying more power at large scales than in the APM galaxy power spectrum measured by Baugh & Efstathiou. We split the QSO sample into two redshift bins and find little evolution in the amplitude of the power spectrum, consistent with the result for the QSO correlation function. In models with m �0.1 this represents evidence for a QSO-mass bias that evolves as a function of time. The QSO power spectrum may show a spike feature at � 90h 1 Mpc assuming thecosmology or � 65h 1 Mpc assuming an EdS cosmology. Although the spike appears to reproduce in both the North and South strips and in two independent redshift ranges, its statistical significance is still marginal and more data is needed to test further its reality. We compare the QSO power spectra to CDM models to obtain a constraint on the shape parameter, . For two choices of cosmology ( m=1, �=0 and m=0.3, �=0.7), we find the best fit model has � 0.1 ± 0.1. In addition, we have shown that a power spectrum analysis of the Hubble VolumeCDM mock QSO catalogues with = 0 .17 as input, produces a result which is statistically consistent with the data. The analysis of the mock catalogues also indicates that the above results for are unlikely to be dominated by systematic effects due to the current catalogue window. We conclude that the form of the QSO power spectrum shows large-scale power significantly in excess of the standard CDM prediction, similar to that seen in local galaxy surveys at intermediate scales.