From: Serena Nobili (serena@physto.se)
Date: Fri Jan 30 2004 - 05:52:00 PST
Dear Greg,
I have done some work to try to answer some of your questions concerning
the analysis carried in Section 6 of the paper (see below).
I have run some tests to check how much of that analysis depends on the
intrinsic colors and correlation I assumed (i.e. as in Nobili et al. 2003)
I have run my programs assuming zero correlation between colors at
different epochs, and/or assuming different values for the intrinsic
dispersion. For each of the configuration (no-correlation, intrinsic
dispersion) I have computed the chisq of the high-z SNe to the nearby
distribution, and to the dust models. I reported the results in the paper
web page:
http://www.physto.se/~snova/internal/papers/iband/#dust
The conclusion of these tests is that the analysis does not depend
critically on the assumptions on correlation and intrinsic colors.
The main reason why we get a different result than Riess et al (2000), is
the spread of the 3 high-z SNe used. What he did, is to use one single
supernova, with very blue colors to put limit on the reddening by gray
dust.
I hope this helps.
Cheers
Serena
On Thu, 15 Jan 2004, Serena Nobili wrote:
>
>9) Greg Aldering expressed his worry again for the case of 1999Q in
>the analysis of Section 6 (colors and grey dust). We discussed the
>reasons why we get different results than Riess for the test on grey
>dust based on B-I colors. These are the correlation between the data
>of the same SN, the different B-I versus time used in our analysis,
>the different K-corrections, and the fact we assume stretch=1 for
>it. Knowing the stretch of this SN would help in feeling more
>confident (see point 7 above). Greg also worries about the correlation
>between colors at different epochs, calculated in Nobili et al
>2003. It has been proposed for people to read the paper. Also, Greg
>needs to think about it and perhaps suggest tests or plots which would
>make him more confident in the analysis. Ariel pointed out that Riess
>claims this SN to be too blue, but we don't see that in Figure 16 of
>the paper.
>
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