From: Robert A. Knop Jr. (robert.a.knop@vanderbilt.edu)
Date: Thu Mar 20 2003 - 04:53:52 PST
P99 was *not* assuming a U-B at Bmax of -0.2, as I had previously
thought. I had assumed this since this is the color that Peter's
uberspectrum gives. However, Peter's uberspectrum was not what we used
for the P99 K-corrections; rather, we used a set of spline
interpolations produced by Don based on input data from Peter. I
suspect, however, that that input data was different from what Peter
would later get from his uberspectrum.
One can't directly extract the colors assumed in the spectra from the
spline files used for P99. However, by taking differences of the
K-corrections in the redshift range where they overlap, one can deduce
what colors were assume. Below are the differences between the U to R
and the B to R K-corrections for s=1 supernova at t=0. This should be
the U-B color which was assumed going into the template. The redshift
range shown is the range where the two K-correction spline files
overlap:
at z=0.5, u-b = -0.304869
at z=0.52, u-b = -0.307014
at z=0.54, u-b = -0.31019
at z=0.56, u-b = -0.314221
at z=0.58, u-b = -0.314597
at z=0.6, u-b = -0.318243
at z=0.62, u-b = -0.3207
at z=0.64, u-b = -0.321136
at z=0.66, u-b = -0.329953
at z=0.68, u-b = -0.32699
In other words, it looks like P99 was assuming a U-B color at Bmax
closer to -0.3 or -0.32 than the -0.2 I'd thought previously.
I also have come to the *very* firm belief that we wildly underestimated
the K-correct/template systematic uncertainty in P99, and that we are
likely to do so again.
-Rob
-- --Prof. Robert Knop Department of Physics & Astronomy, Vanderbilt University robert.a.knop@vanderbilt.edu
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