Craig Markwardt wrote in message ...
In a given analysis, there is only one light curve template, and it is
based on the nearby supernova remnant sample. The "stretch factor" s
is introduced to match an individual light curve to the template, with
the understanding that individual supernova light curves can be
slightly slower or faster than the mean.
There would be evidence of bias if the fitting of the light curve
profiles treated the nearby and high-z supernovae separately. BUT,
they were NOT. Both the samples were fitted with the same function,
including a stretch factor. [ref. 1, Tables 1 & 3]
There would be evidence of bias if the fitting of the light curve
profiles allowed only a stretch but not a compression. BUT, they did
NOT. Both stretched and compressed light curves were permitted in the
fitting, and in fact some moderate-z light curves evolved faster than
local ones as a result. [ref. 1, Tables 1 & 3] However, on *average*,
the high-z supernova light curves evolve much more slowly. [ref. 1,
References
1. Goldhaber, et al. 2001, ApJ, 558, 359
It is Goldhaber himself who has put the time dilation into the SN
data by introducing a stretch s proportional to redshift. Take out
the stretch from the data (and the k correction to B,and the
template fits to R or parab-18) and the apparent time dilation will
disappear.
The closest available data that I can find, supplied by Goldhaber
seems to be fig 1a and 1b which do not have the k correction or
stretch but do have a template fit to R.? If there were a
lightcurve or table of the SN data without this template fit to
parab-18 for both the C-T and SCP SN data, I am sure that the
apparent `time dilation` would disappear and what would remain
would be only a range of lightcurves reflecting the various different
restframe emission wavelengths of the SN`s studied. However, its
not that clear to me what the filter bands the observations were
made in but I believe that its R band observed for all the SCP
SN`S and B band observed for all the C-T SN`s. These then appear
to have been fitted to R and B band templates respectively. You
may possibly be able to clarify this part of the process a
bit more.
One question here regarding 2 SN`s from Knop may provide an answer
as to why even with the s factored in, Knops` results still favor
no time dilation...Why do you 1998ay and 1998be have different
`s` values applied? The two lightcurves graphs are
distinctinctly different from each other with 1998be having
faster decays in both I and R. The stretch value s in the
table 3 Knop is also different for each. 1998ay is s=1.04
while 1998be is s=0.8. Yet they are both the same redshift
at z=0.64 . I would have thought that the same stretch factor s
would be applied to both SN`s seeing as they both have the
same redshift.
Sean
(My apologies to Steve W. In my last post I incorrectly stated
that 1998as is z=0.85 when in fact its 0.35. Sorry)