From: Chris Lidman (clidman@eso.org)
Date: Wed Mar 03 2004 - 15:45:06 PST
Hi Serena,
Thanks for the reply. I am replying to this without having had a
chance to look at your new plots (by the way, I think that you do a
great job in making these plots available).
I have a few follow-up comments.
> >Note that these plots are quite flat, which would argue that the
> >light curve shape is not all that important in determining the peak
> >magnitude.
> >
> >
>
> I must disagree with this point. The flatness of these plots is only
> telling us that the I-band light curve shape is not correlated with the
> B-band stretch factor, and not that the Imax is not correlated with the
> I-band light curve shape. I would rather say, that there is some light
> curve shape parametrization that we did not find yet. Do you see what I
> mean?
>
Yes, I do. Good point.
>
> >In relation to the numbered items.
> >
> >1) There was concern for the way the dispersion in the Hubble diagram
> > is computed. Serena should compute the weighted r.m.s.
> >
> >Serena's reply ...
> >
> >I have done this. The weighted r.m.s. gives about the same values as
> >the non-weighted r.m.s. due to the uncertainties, which are about the same
> >for all the points. However, Table 4 now includes the weighted r.m.s. as
> >well as the weighted average for each of the samples. I have also added a
> >discussion in section 3 about the differences between the data sets.
> >
> >Chris' comment ...
> >
> >I think that we were also interested in seeing the RMS scatter about
> >the individual Hubble lines and not the scatter about the Hubble line
> >that is derived from the entire data set. Was the RMS calculated in
> >this way? It is not 100% clear in the paper.
> >
>
> I think the mean value of the residuals for each data set (column 4 of
> Table 4) should be taken as an indication that differences are not
> important. Although I could run the fit on each data set separately, I
> don't think this is really relevant, given the low statistics of each of
> them separately, e.g. only 6 SNe are in the CfA sample. For the same
> reason I think any claims on differences between the data sets
> (which I don't clearly see anyway), should be done very carefully.
>
Nevertheless, I think it should be done. I understand that the sample
size is small, but I expect that you'll find that the RMS for the
Calan/Tololo sample will show a significant decrease. I do not
expect there to be much of a change for the CfA and CfA2 samples.
> >10) Serena will try to add the restframe B,V-band for 1999Q, reduced by
> > Vitaliy, in the analysis presented in Section 6.
> >
> >Serena's reply ...
> >
> >This is interesting! It turned out that the fit obtained by SNMINUIT
> >fixing the time of B-maximum to Tonry value, would give a color excess
> >E(B-V) = 0.2 mag (see email by Vitaliy in the archive on Feb 12). Given
> >that this SN is host-less, this value is very surprising. I have been
> >playing with numbers and plots. If the B-band stretch factor was sB=0.82
> >the colors would make perfectly sense (even in I-band). Unfortunately the
> >stretch fitted by SNMINUIT is 1.061 instead. Check plots and discussion
> >in:
> >
> >http://www.physto.se/~snova/internal/papers/iband/index.new.html#99q
> >
> >Giving all of this, I do not think we should add the B-V colors of SN1999Q
> >in the analysis of section 6.
> >
> >Chris's comments
> >Would the colour of 99Q be normal if the date of maximum derived by
> >Vitaliy was used instead?
> >
>
> I have added one plot about that in the web page (Figure B)
>
> http://www.physto.se/~snova/internal/papers/iband/#99q
>
> The situation does not look much better, unfortunately.
>
> Please, let me know if you have more doubts or comments.
> Cheers
>
I think that we should include the B-V colour of SN99Q in the analysis.
If the analysis tells us that E(B-V) is 0.2, then so be it. Unless, we
think that there is something wrong or suspect with this SNe, then
we should show the full data set.
The stretch that Vitaliy finds, s~1.1 is certainly consistent with the
idea that this SNe is hostless. What are the errors on the B-V colour.
If it similar to the other two, then I do not see an inconsistency.
Cheers, Chris.
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