From: Pilar Ruiz-Lapuente (pilar@MPA-Garching.MPG.DE)
Date: Fri May 02 2003 - 17:19:12 PDT
Dear Rob,
The paper is really in very good shape. It provides an excellent
explanation on all what has been done. It is cristal--clear!
I would like for the moment to suggest an improvement to the
section: Supernova Population Drift.
In the second paragraph you address the suggested dependence of
SNe Ia properties with metallicity. I think it would make a better
case if you place together everything that refers to the alleged
metallicity dependence. It means to merge two separate sentences.
"On the theoretical side, SN formation models by Kobayashi et al.
(1998); Nomoto, Nakamura, \& Kobayashi (1999) suggest that the
progenitor binary system must have [Fe/H] > -1 in order to produce
a SN Ia. This would impose a lower limit to the metallicities of all
SNe Ia, and thus limit the extent of any metallicity--induced brightness
differences between high and low--redshift SNe Ia. On the empirical side,
the lack of gradient in the intrinsic luminosities of SNe Ia with
galactocentric distance, couple with the fact that metallicity gradients are
common in spiral galaxies (Henry \& Worthey 1999), lead Ivanov, Hamuy,
\& Pinto (2000) to suggest that metallicty is not a key parameter in
controlling SNe Ia brightnesses at optical wavelengths. In addition,
Hamuy et al. (2000); Hamuy et al. (2001) find that lightcurve width is not
dependent on host galaxy metallicity."
(Merging like this gives all the account on the metallicity issue in
a spot, so it is less scattered. A question: is there something by
Quimby et al also on that? If so, I would include it
in the same paragraph).
Then I would mention other possibilities related to population age. In a
next paragraph one could continue:
"Alternatively a population age effect
linked to the pre--explosion cooling undergone by the WD and its effect
in the initial burning conditions has been suggested together with
other population age effects linked to the mass of the
primary exploding WD (see for a review Ruiz--Lapuente 2003).
As the local sample of SNe Ia represents SNe Ia of all ages and
metallicity, both effects (metallicity and population age) can be
studied locally. The low--redshift studies present data suggesting that
SNe Ia intrinsic luminosities (i.e.prior to stretch correction) may
correlated with host galaxy environment (Hamuy et al. 1996; ....(continuing
text till R99). These findings are actually encouraging, since
unlike stretch itself, there is some hope that host--galaxy environment
variations can be translated into physical parameters information.
More importantly for cosmology, R99 used their......
little effect on whether the resulting SN can be standarized. "
Last paragraph as it is.
Reference.
Ruiz-Lapuente, P. 2003 in "3K, SNs, Clusters: Hunting the Cosmological
Parameters", ed. D. Barbosa et al. (Kluwer Acad. Publ.). astro-ph/0304108
Congratulations Rob. After reading the Tonry et al. paper, it was
not what many of us expected. The SCP paper is certainly much more
impacting.
Cheers! Pilar
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