Implications of 2dFGRS results on cosmic structure

Abstract

The 2dF Galaxy Redshift Survey is the first to observe more than 100,000 redshifts, making possible precise measurements of many aspects of galaxy clustering. The spatial distribution of galaxies can be studied as a function of galaxy spectral type, and also of broad-band colour. Redshift-space distortions are detected with a high degree of significance, confirming the detailed Kaiser distortion from large-scale infall velocities, and measuring the distortion parameter beta = Omega_m^{0.6}/b = 0.49 +- 0.09. The power spectrum is measured to <10% accuracy for k > 0.02 h Mpc^{-1}, and is well fitted by a CDM model with Omega_m h =0.18 +- 0.02 and a baryon fraction of 0.17 +- 0.06. A joint analysis with CMB data requires Omega_m = 0.31 +- 0.05 and h = 0.67 +- 0.04, assuming scalar fluctuations. The fluctuation amplitude from the CMB is sigma_8 = 0.76 +- 0.04, assuming reionization at z < approx 10, so that the general level of galaxy clustering is approximately unbiased, in agreement with an internal bispectrum analysis. Luminosity dependence of clustering is however detected at high significance, and is well described by a relative bias of b/b^* = 0.85 + 0.15(L/L^*). This is consistent with the observation that L^* in rich clusters is brighter than the global value by 0.28 +- 0.08 mag.