Ho from Type Ia Supernovae

Abstract

The Hubble diagrams in B, V, and I of a complete sample of 35 SNeIa with (B-V) < 0.06 and 1200 < v < 30000 kms^{-1} have a scatter of only 0.1 mag, after small corrections are applied for differences in decline rate Delta m_{15} and color (B-V). The tightness of the Hubble diagrams proves blue SNeIa to be the best ``standard candles&#39;&#39; known. Their absolute magnitudes M_{B,V,I} are calibrated by eight SNeIa with Cepheid distances from HST. Combining this calibration with the appropriate Hubble diagrams yields a large-scale value of H_0 = 58.5+/-6.3 at the 90-percent confidence level. The Hubble diagram of SNeIa has so small scatter that it seems feasable to determine Lambda ``locally&#39;&#39;, i.e. within z<0.12, once 100-200 SNeIa with good photometry will be available. Such a local determination would minimize evolutionary effects and K-term corrections.