The m–z relation for Type Ia supernovae, locally inhomogeneous cosmological models, and the nature of dark matter

Abstract

The m–z relation for Type Ia supernovae is one of the key pieces of evidence supporting the cosmological ‘concordance model’ with λ₀ ≈ 0.7 and Ω₀ ≈ 0.3. However, it is well known that the m–z relation depends not only on λ₀ and Ω₀ (with H₀ as a scale factor) but also on the density of matter along the line of sight, which is not necessarily the same as the large-scale density. I investigate to what extent the measurement of λ₀ and Ω₀ depends on this density when it is characterized by the parameter η (0 ≤ η ≤ 1), which describes the ratio of density along the line of sight to the overall density. I also discuss what constraints can be placed on η, both with and without constraints on λ₀ and Ω₀ in addition to those from the m–z relation for Type Ia supernovae.

supernovae: general, cosmological parameters, cosmology: theory, dark energy, dark matter