Details

Autor(en) / Beteiligte

• Erdogdu, Pirin
• Ettori, Stefano
• Lahav, Ofer

Titel

‘Hyper-parameters’ approach to joint estimation: applications to Cepheid-calibrated distances and X-ray clusters

Ist Teil von

• Monthly notices of the Royal Astronomical Society, 2003-04, Vol.340 (2), p.573-579

Ort / Verlag

Oxford, UK: Blackwell Science Ltd

Erscheinungsjahr

2003

Quelle

Wiley-Blackwell Journals

Beschreibungen/Notizen

• We use a generalized procedure for the combined likelihood analysis of different cosmological probes, the ‘hyper-parameters’ method, that allows freedom in the relative weights of the raw measurements. We perform a joint analysis of the Cepheid-calibrated data from the Hubble Space Telescope Key Project and the baryon mass fraction in clusters to constrain the total matter density of the Universe, Ωm, and the Hubble parameter, h. We compare the results obtained using the hyper-parameters method with the estimates from standard χ2 analysis. We assume that the Universe is spatially flat, with a cosmological constant. We adopt the big bang nucleosynthesis constraint for the baryon density, assuming the uncertainty is Gaussian distributed. Using this and the cluster baryon fraction data, we find that the matter density and the Hubble constant are correlated, Ωmh0.5≈ 0.25, with preference for a very high h. To break the degeneracy, we add in the Cepheid-calibrated data and find the best-fitting values (Ωm, h) = (0.26+0.06−0.06, 0.72+0.04−0.02) (68 per cent confidence limits) using the hyper-parameters approach. We use the derived hyper-parameters to ‘grade’ the six different data sets we analyse. Although our analysis is free of assumptions about the power spectrum of fluctuations, our results are in agreement with the Λ cold dark matter ‘concordance’ parameters derived from the cosmic microwave background anisotropies combined with Type Ia supernovae, redshift surveys and other probes.