Distance Scale from Supernovae

Abstract

Supernovae have been playing an ever increasing role in the determination of the key cosmological parameters. They are extremely luminous point sources whose brightness at maximum rivals that of their host galaxies and thus can be observed at cosmologically significant distances. That SNe Ia could be used as standard candles has been proposed for many years. However, most of the progress in this field has occured over the last decade. Extensive ground-based surveys have identified a large number of new supernovae and characterized their global properties in a statistically meaningful way. At the same time, using the Hubble Space Telescope, a team led by Sandage has carried out an extensive program to determine the absolute brightness of a selected sample of supernovae. This has allowed the Hubble diagram for SNe Ia to be placed on an absolute scale and the Hubble constant itself to be determined with a precision of 10% or better. We review the current work in this field and discuss the main effects that influence the determination of the absolute brightness at maximum for SNe Ia. We show that the best values are M _B = −19.50 ± 0.06 and M _V = −19.49 ± 0.06. The derived value for the Hubble constant is H ₀ = 59 ± 6 km s ⁻¹ Mpc ⁻¹. We also review the exciting new results for the values of the cosmological constants derived using high-redshift SNe Ia. Preliminary results suggest a non-empty inflationary Universe with parameters lying along the line determined by 1.34Ω _M − Ω_Λ = −0.45.

On assignment from the Space Science Department of ESA