From: Alex Conley (aconley@panisse.lbl.gov)
Date: Thu Mar 11 2004 - 11:16:14 PST
On Thu, 11 Mar 2004, Robert A. Knop Jr. wrote:
> ...well, mine shouldn't be *too* far off in I. I think that the
> differences are ca. 0.05 between mine and Serena's, which sounds
> plausible to me.
The difference is about 0.05 (see the second email in this thread for a
plot), and it sounds like Lifan is further off, but I think that the
comparison has lost a lot of strength as a tie breaker. So we may be
back to waiting for Lifan to explain what he is actually doing in more
detail.
> I think the worry is, though, that for the I-band there are specific
> features that make a bigger difference-- and perhaps the spectra Peter
> chose to build his original uberspectra didn't have "typical" enough
> features.
Yeah, most people seem to think that this is the problem.
I again want to emphasize that this is a bigger difference than it sounds
like. From the standpoint of Serena's paper it probably isn't a big deal,
but if someday we have 20 high-z I band SNe it is critical that we
understand this better. Assigning the 0.05 as an additional error bar is
completely bogus because it is very strongly correlated between different
SNe and is also a function of redshift. The net effect is quite
significant -- much greater than just giving everything a slightly larger
error bar would create.
This is one of the big issues that I have been struggling with in CMAGIC
-- when I use Serena's K-corrections for B vs. B-V CMAGIC, the
cosmological contours shift by a sigma or more along the short axis.
From this discussion it sounds like this shouldn't worry me too much
because Serena doesn't fully trust her own U band, and I have a lot of
filter mismatches that drag some U band into the B band.
Alex
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