From: clidman (clidman@eso.org)
Date: Sun Jul 20 2003 - 15:34:24 PDT
Hi Gaston,
I've read through all the material and there are two points I'd like to discuss
during tomorrow's teleconference.
EW versus Absolute Magnitude
============================
I like very much the idea of plotting spectroscopicly defined
quantities against absolute magnitude rather than Delta m15 or
stretch, as this is directly related to the issue we are interested
in. Namely, can we use spectroscopic features to tell us something
about the luminosity of the SNe. In this way, we steer clear of the
issue of what these spectroscopic features tell us about the physics
of type Ia explosions. I also like the idea of limiting this analysis
to spectra that have been taken at similar times. Currently, the
analysis is done for spectra around maximum light. Other windows could
be considered; however, for the interpretation of high z spectra, the spectra
that were taken around maximum light will be the most useful.
From the plots, there is a clear correlation between various spectral
features and luminosity. What is the scatter about a simple linear
regression to some of the plots? The correlation between the SiII ratios
and luminosity looks very tight if one outlier is removed. It looks as
tight as correlation between Delta m15 and luminosity.
By looking at the plots in the first paper, you may want to try
correlating an index that is made up from indices 7 + 4 + 6 + 2 or
7 + 4 + 6 or 2 + 4 with absolute magnitude. These four indices appear
to have the strongest correlation with luminosity. For high z SNe, a
plot with 2 + 4 would be the most useful.
Definition of Indices
=====================
The definition of the indices is still a bit vague. We need to
describe in recipe on how these indices are measured so that anyone can
repeat the measurement.
As yet , I do not have a number to which people can call. If Ido not have anything
by tomorrow morning, I'll try to set something up in Santiago.
Cheers, Chris.
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