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Evidence for a non-zero and a low matter density from a combined analysis of the 2dF Galaxy Redshift Survey and cosmic microwave background anisotropies

G. Efstathiou1Institute of Astronomy, Madingley Road, Cambridge CB3 0HAStephen J. MoodyInstitute of Astronomy, Madingley Road, Cambridge CB3 0HAJ. A. PeacockInstitute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJWill J. Percival3Institute for Astronomy, University of Edinburgh Royal Observatory, Blackford Hill, Edinburgh EH9 3HJC. M. BaughDepartment of Physics, University of Durham, South Road, Durham DH1 3LEJoss Bland‐HawthornAnglo-Australian Observatory, PO Box 296, Epping, NSW 2121, AustraliaTerry BridgesAnglo-Australian Observatory, PO Box 296, Epping, NSW 2121, AustraliaRussell CannonAnglo-Australian Observatory, PO Box 296, Epping, NSW 2121, AustraliaShaun ColeDepartment of Physics, University of Durham, South Road, Durham DH1 3LEMatthew CollessResearch School of Astronomy and Astrophysics, The Australian National University, Weston Creek, ACT 2611, AustraliaC. A. CollinsAstrophysics Research Institute, Liverpool John Moores University, Twelve Quays House, Birkenhead L14 1LDW. J. CouchDepartment of Astrophysics, University of New South Wales, Sydney, NSW 2052, AustraliaGavin DaltonAstrophysics, Nuclear and Astrophysics Laboratory, University of Oxford, Keble Road, Oxford OX1 3RHRoberto De ProprisDepartment of Astrophysics, University of New South Wales, Sydney, NSW 2052, AustraliaSimon P. DriverSchool of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife KY6 9SSRichard S. EllisDepartment of Astronomy, Caltech, Pasadena, CA 91125, USACarlos S. FrenkDepartment of Physics, University of Durham, South Road, Durham DH1 3LEKarl GlazebrookDepartment of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218-2686, USACarole JacksonResearch School of Astronomy and Astrophysics, The Australian National University, Weston Creek, ACT 2611, AustraliaO. LahavInstitute of Astronomy, Madingley Road, Cambridge CB3 0HAIan LewisAnglo-Australian Observatory, PO Box 296, Epping, NSW 2121, AustraliaS. L. LumsdenDepartment of Physics, University of Leeds, Woodhouse Lane, Leeds LS2 9JTS. MaddoxSchool of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RDP. NorbergDepartment of Physics, University of Durham, South Road, Durham DH1 3LEB. A. PetersonResearch School of Astronomy and Astrophysics, The Australian National University, Weston Creek, ACT 2611, AustraliaWilliam J. Sutherland3Institute for Astronomy, University of Edinburgh Royal Observatory, Blackford Hill, Edinburgh EH9 3HJKeith TaylorDepartment of Astronomy, Caltech, Pasadena, CA 91125, USA(The 2dFGRS Team)

2002en

ABI

Annotatsiya

We perform a joint likelihood analysis of the power spectra of the 2dF Galaxy Redshift Survey (2dFGRS) and the cosmic microwave background (CMB) anisotropies under the assumptions that the initial fluctuations were adiabatic, Gaussian and well described by power laws with scalar and tensor indices of ns and nt. On its own, the 2dFGRS sets tight limits on the parameter combination Ωmh, but relatively weak limits on the fraction of the cosmic matter density in baryons Ωb/Ωm. (Here h is Hubble's constant H0 in units of 100 km s−1 Mpc−1. The cosmic densities in baryons, cold dark matter and vacuum energy are denoted by Ωb, Ωc and ΩΛ, respectively. The total matter density is Ωm=Ωb+Ωc and the curvature is fixed by Ωk=1−Ωm−ΩΛ.) The CMB anisotropy data alone set poor constraints on the cosmological constant and Hubble constant because of a ‘geometrical degeneracy’ among parameters. Furthermore, if tensor modes are allowed, the CMB data allow a wide range of values for the physical densities in baryons and cold dark matter (ωb=Ωbh2 and ωc=Ωch2). Combining the CMB and 2dFGRS data sets helps to break both the geometrical and tensor mode degeneracies. The values of the parameters derived here are consistent with the predictions of the simplest models of inflation, with the baryon density derived from primordial nucleosynthesis and with direct measurements of the Hubble parameter. In particular, we find strong evidence for a positive cosmological constant with a ±2σ range of 0.65<ΩΛ<0.85, independently of constraints on ΩΛ derived from Type Ia supernovae.

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DOI: 10.1046/j.1365-8711.2002.05215.x

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