Breaking the Degeneracy of Cosmological Parameters in Galaxy Redshift Surveys

Abstract

The measurement of cosmological parameters is investigated in a representation of the least-action method that uses a redshift-space data set to simultaneously constrain the real-space Ðelds d and This ¿. method is robust in recovering the entire evolution of the matter density contrast and peculiar velocities of galaxies in real space from current galaxy redshift surveys. The main strength of the method is that it permits us to break the degeneracy of the parameters b and (customarily measured in the ratio ) m from redshift-space distortions), and these are evaluated separately in the current context. The b 4 ) m 0.6/b procedure provides a simple numerical means to extract as much information as possible from a given sample, in the simplest linear bias model, before resorting to cosmic complementarity to resolve the degeneracy in the measurement ofThe same premise applies to more sophisticated choices of bias ) m . models. We construct a likelihood parameter to evaluate the relative likelihood of di †erentThe method is applied to the IRAS 1.2 Jy redshift survey with a low-resolution ) m . Gaussian smoothing length of 1200 km s~1 within a spherical region km s~1, and the x max D 15,000 reconstructed velocity Ðeld is then compared with POTENT-reconstructed velocities from the Mark III radial-velocity data set within a radius of D5000 km s~1, which have been suitably prepared to account for Malmquist bias and other systematic errors. The analysis yields a likelihood for the parameters that is overall consistent with and b B 1.1, thus lending support to a nonvanishing cosmological ) m B 0.3 constant in a Ñat universe. ) " B 0.7 Subject headings : cosmology : observations È galaxies : distances and redshifts È large-scale structure of universe

Ω M — Different Ways to Determine the Matter Density of the Universe

“…(2) lists the catalogues used: MARK III and SFI are catalogues of galaxies, Abell is a catalogue of galaxy clusters. Willick & Strauss (1998) MARK III Ωm ≈ 0.3 Susperregi (2001) MARK III Ωm ≈ 0.3 Zaroubi et al (1997) MARK III Ωm = 0.5 ± 0.1 Freudling et al (1999) SFI Ωm = 0.5 ± 0.1 Bridle et al (2001) SFI 0.25 < Ωm < 0.89 Sigad et al (1998) MARK III Ωm ≈ 1 Branchini et al (2000) Abell Ωm ≈ 1 Carlberg et al (1997b) inferred mass-to-light ratios from the CNOC sample. They could also measure directly with their data the value for the field luminosity density.…”

Astrophysics in 2001

“…Unchanged for some years now is the agreement among several methods that the total matter density of the universe amounts to about , or so. So also this year Q p 0.3 ‫50.0ע‬ m say Miller et al (2001b, who note that they have been able to make a smooth connection between power spectra of the density distributions determined from the microwave background radiation and from galaxy catalogues), Susperregi (2001) and Peacock et al (2001), both based on large structure, the latter including the new 2dF database, and Hoekstra et al (2001a), a result from weak lensing by small groups of galaxies. But, if once again you have time for only one, a paper that brings together data from the CMB, from Type Ia supernovae, and from large scale structure is Bridle et al (2001) The age had better be larger than any other age found for objects in the universe.…”

Peculiar velocity reconstruction with the fast action method: tests on mock redshift surveys

“…Shaya et al 1995) relied on iterations. However, self‐consistent treatments of the problem have been proposed by Schmoldt & Saha (1998), Nusser & Branchini (2000), Phleps (2000), Susperregi (2001) and Goldberg (2001).…”