![]() In the era of precision cosmology among others, the scientific goals of research using galaxy redshift surveys are gradually shifting from inferring a set of values of cosmological parameters using galaxy as their probes to understanding the origin and evolution of galaxy distribution given a set of parameters accurately determined by the other probes like CMB and supernovae. Thus we can now directly address the evolution of visible objects from the analysis of their redshift surveys separately from the nonlinear growth of the underlying dark matter gravitational potentials. In fact, we even have very accurate and useful analytic formulae to describe the evolution deep in its nonlinear regime. In addition, extensive numerical simulations of structure formation in the Universe has significantly advanced our understanding of the gravitational evolution of the dark matter component in the standard gravitational instability picture. Gravitational growth of dark matter component is well understood: In a sense, the origin of the Universe at z ≈ 1000 and the evolution of the Universe after the epoch are now equally important, but they constitute well separable questions that particle and observational cosmologists focus on, respectively. This may be taken as the initial condition of the Universe from the point-of-view of the structure evolution toward z = 0. The first-year WMAP (Wilkinson Microwave Anisotropy Probe) data among others have established a set of cosmological parameters. The Universe at z ≈ 1000 is well specified: These unprecedented numbers of the objects as well as the homogeneous selection criteria enable the precise statistical analysis of their distribution. The numbers of galaxies and quasars in the spectroscopic sample of Two Degree Field (2dF) are ∼ 250, 000 and ∼ 30, 000, and will reach ∼ 800,000 and 100, 000 upon completion of the on-going Sloan Digital Sky Survey (SDSS). Redshift surveys have unprecedented quantity and quality: Still galaxy redshift surveys are of vital importance in cosmology in the 21st century for various reasons: Indeed one may phrase that the modern observational cosmology started with a sort of galaxy redshift survey by Edwin Hubble. Undoubtedly gamma-rays, neutrinos, and gravitational radiation will join the above already crowded list.Īmong those, optical galaxy redshift surveys are the most classical. Nowadays the exploration of the Universe can be performed by a variety of observational probes and methods over a wide range of the wavelengths: the temperature anisotropy map of the cosmic microwave background (CMB), the Hubble diagrams of nearby galaxies and distant Type Ia supernovae, wide-field photometric and spectroscopic surveys of galaxies, the power spectrum and abundances of galaxy clusters in optical and X-ray bands combined with the radio observation through the Sunyaev-Zel’dovich effect, deep surveys of galaxies in sub-mm, infrared, and optical bands, quasar surveys in radio and optical, strong and weak lensing of distant galaxies and quasars, high-energy cosmic rays, and so on.
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