Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.mrao.cam.ac.uk/~anthony/latex/Gibson.ps Дата изменения: Sun May 21 18:22:32 2000 Дата индексирования: Tue Oct 2 02:42:47 2012 Кодировка: Поисковые слова: cepheid

Type Ia Supernovae and the
Value of the Hubble Constant
Brad K. Gibson
University of Colorado & Swinburne University
Type Ia supernovae (SNe) play a particularly prominent role in
establishing the extragalactic distance scale. As secondary dis-
tance indicators, they stand part from many of their competitors,
due to (a) their ability to probe a regime in which complications
due to the local ow eld are minor, and (b) an exceedingly small
intrinsic dispersion in the distribution of their (corrected) peak lu-
minosities. Eight nearby Type Ia SNe-host galaxies have now had
their distances determined via HST-observed Cepheids, providing
an absolute calibration to the far-eld SN Hubble Diagram, which
in turn provides a (presumably!) accurate determination of the
Hubble Constant H0 .
Of immediate concern is the extant 10% systematic uncertainty
between the analyses of Gibson et al. and Saha et al., in the
sense of a smaller H0 being favored by the latter group. I will
describe exactly where and why this systematic 10% oset origi-
nates, as this remains a matter of confusion for many in the eld.
I will also draw particular attention to several unappreciated com-
plications in the analyses of not only the nearby calibrators, but
also those encountered in constructing an appropriate far-eld SN
Hubble Diagram for use in deriving H0 . An honest appraisal of
the strengths and weaknesses of using Type Ia SNe to derive H0
can be expected!
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