and Cosmology

8.1 Redshift Surveys of Galaxies
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Fig. 8.4. Left: the power spectrum of galaxies is displayed,
as determined from different galaxy surveys, where Δ 2 (k) ∝
k 3 P(k) is a dimensionless description of the power spectrum.
Right: model spectra for Δ(k) are plotted, where Γ varies
from 0.5 (uppermost curve) to 0.2; the data from the various
surveys have been suitably averaged. We see that a value of
Γ ∼ 0.25 for the shape parameter fits the observations quite
well
Fig. 8.5. Left: power spectrum of the galaxy distribution as
measured in the 2dFGRS (points with error bars), here represented
as Δ 2 (k) ∝ k 3 P(k). The curves show power spectra
from CDM models with different shape parameter Γ = Ω m h,
and two values of Ω b : one as obtained from primordial nucleosynthesis
(BBN, solid curves), and the other for models
without baryons (dashed curves). The Hubble constant h = 0.7
and the slope n s = 1 of the primordial power spectrum were
assumed. A very good fit to the observational data is obtained
for Γ ≈ 0.2 (from Peacock, 2003, astro-ph/0309240). Right:
confidence contours in the Ω m h–Ω b /Ω m -plane. Two regions
in parameter space are seen to provide good fits to the data.
The upper region is incompatible with many other cosmological
data. In contrast, the lower left domain in parameter space
is in remarkable agreement with measurements from BBN
(see Sect. 4.4.4), with the baryon fraction in clusters of galaxies
(see Sect. 8.2.3), and with CMB anisotropy measurements
(see Sect. 8.6)