Citation:
Date Published:
March 1, 2007Abstract:
We present a Fourier analysis of the clustering of galaxies in thecombined main galaxy and LRG SDSS DR5 sample. The aim of our analysis isto consider how well we can measure the cosmological matter densityusing the signature of the horizon at matter-radiation equality embeddedin the large-scale power spectrum. The new data constrain the powerspectrum on scales 100-600 h-1 Mpc with significantly higherprecision than previous analyses of just the SDSS main galaxies, due toour larger sample and the inclusion of the LRGs. This improvement meansthat we can now reveal a discrepancy between the shape of the measuredpower and linear CDM models on scales 0.01 hMpc-1-1, with linear model fitsfavoring a lower matter density (ΩM=0.22+/-0.04) onscales 0.01 h Mpc-1-1 and ahigher matter density (ΩM=0.32+/-0.01) when smallerscales are included, assuming a flat ΛCDM model with h=0.73 andns=0.96. This discrepancy could be explained byscale-dependent bias, and by analyzing subsamples of galaxies, we findthat the ratio of small-scale to large-scale power increases with galaxyluminosity, so all of the SDSS galaxies cannot trace the same powerspectrum shape over 0.01 h Mpc-1-1. However, the data are insufficient to clearly show aluminosity-dependent change in the largest scale at which a significantincrease in clustering is observed, although they do not rule out suchan effect. Significant scale-dependent galaxy bias on large scales,which changes with the r-band luminosity of the galaxies, couldpotentially explain differences in our ΩM estimates anddifferences previously observed between 2dFGRS and SDSS power spectraand the resulting parameter constraints.