From: Ariel Goobar (ariel@physto.se)
Date: Tue Aug 31 2004 - 02:46:35 PDT
Hi Alex,
I am reading with great interest your documentation on the CMAGIC
analysis. I
think it is a really nice piece of work. There are a few questions that
I have
right now, maybe I'll have more by the end of the week.
1) As I understand it, you correct for MW extinction. Have you
considered
the idea of using the "known" MW extinction for tests the CMAGIC
method
versus the standard analysis? Eg, one could perhaps look for what the
MW dust does to the low-z dispersion in both methods and thus check
that the lower sensitivity to extinction for CMAGIC holds. Maybe this
could be extended to the best measured high-z SNe.
2) It does seem a bit awkward that you are very systematic about your
data cuts
but yet make "case by case" decisions about what kind of LC-fits you
use (i.e B&V together or fitted separately). Especially, as you point
out, the "choice" will not work the same way for low and high-z
fits. I suggest you stick to one strategy for all lightcurves
and estimate the associated systematic error based on what you would
have found if you would have taken the "other" track. I am sure you
have considered this. Why did you decide not to?
3) The two populations in the high-z residuals seem like a real concern
to me. If the explanation has indeed to do with host galaxy
extinction
(as I think you advocate), shouldn't you be able to see hints of
that in
the residual dispersion in CMAG vs standard, i.e from graphs like in
Fig 31 in your method doc? I guess additional tests could be provided
with simulations as in Commins et al.
4) Have you considered quantifying the bias from possible intergalactic
dust?
If you want, I can help you with synthetic data sets.
Cheers,
Ariel
-- ___________________________________________________________________ Ariel Goobar (www.physto.se/~ariel) Department of Physics, Stockholm University AlbaNova University Center, SE-106 91 Stockholm, SWEDEN tel: +46 8 55378659 fax: +46 8 55378601
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