Redshift-space distortions in the PSCz galaxy catalogue

Astronomy and Astrophysics – Astronomy

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Cosmology: Theory, Dark Matter, Large-Scale Structure Of Universe

Scientific paper

We apply a spherical harmonic analysis to the Point Source Redshift Survey (PSCz), to compute the real-space galaxy power spectrum and the degree of redshift distortion caused by peculiar velocities. We employ new parameter eigenvector and hierarchical data compression techniques, allowing a much larger number of harmonic modes to be included, and correspondingly smaller error bars. Using 4644 harmonic modes, compressed to 2278, we find that the IRAS redshift-space distortion parameter is β=0.39-0.12+0.14 and the amplitude of galaxy clustering on a scale of k=0.1hMpc-1 is Δg,0.1=0.42+/-0.02. Combining these we find the amplitude of mass perturbations is Δm,0.1=(0.16+/-0.04)Ωm-0.6. While this is compatible with results from the cosmic microwave background (CMB), with a small degree of tilt, it disagrees with the amplitude of matter perturbations estimated from the abundance of clusters by a factor of 2, independent of cosmology. A preliminary model fitting analysis combining the CMB with either the PSCz or cluster abundances shows that the cosmological matter density parameter Ωm=0.29+/-0.09, and the IRAS bias parameter b=1.22+/-0.28. However, the cluster abundances suggest that Δm,0.1=0.60+/-0.09 and ns=0.96+/-0.03, while the PSCz requires Δm,0.1=0.34+/-0.05 and ns=0.81+/-0.05. Given the physics of galaxy formation is poorly constrained, we conclude that IRAS galaxies and mass are only partially correlated.

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