From: Richard Ellis (rse@astro.caltech.edu)
Date: Thu May 01 2003 - 08:50:39 PDT
Dear Rob et al:
I have followed the HST paper developments as best I could and very
much like the final product. It is clearly very thorough and Rob
is to be congratulated. I certainly have no objection to it being
submitted as is.
Since I am travelling, I offer only one major comment at this late
stage and that is that I think it is wise to do a better job of
cross-referencing and comparing with Sullivan et al. There is a
clear overlap in some of the goals even if the methodology
is very different. Sullivan et al is only obliquely mentioned
at the very end of the paper yet, in my humble opinion, it
is the only other major SCP paper with new data since P99. It
seems odd therefore that we don't take the trouble to present
all three papers as part of a logical sequence.
How could this be done?
I would insert a new paragraph in Section 1 ahead of "In this
paper" which tells the next part of the story post-P99. This
would describe the Sullivan et al approach to look for evidence
that dust is distorting the Hubble diagram and succinctly
say what was found. This then gives you the opportunity to
say it is not as convincing perhaps as a direct measurement
of the reddening of each SN which is the next logical step.
In Section 2.1, we cannot simply ignore the fact
that Sullivan et al did not categorize any of the present
sample morphologically. The dates of the WFPC2 observations
and the Sullivan et al paper make this something readers
will be very puzzled about. I don't know what it best to
say here. I did push this "orphan SNe" issue quite hard last
summer.
In Section 2.2, We ought to be clearer in discussing how the
local SNe have been selected (Table 5). Recall that
in Sullivan et al we re-analyzed the enlarged Hamuy et al/Riess
sample over and above that in P99 with SCP precepts. This was
discussed in some detail, as well as reconsideration of some
of the P99 data. Again, we can't pretend that discussion never
occurred.
Table 7 and Figure 1 likewise present E(B-V) comparisons which
overlap with similar plots given in Sullivan et al. The natural
way to link the two papers would be to compare and contrast
the results in a subsection of Section 3. It would be trivial
to morphologically classify the hosts of these 11 SNe and
enlarge the comparison. I refer you to Figure 10 (I think,
no internet here in Tucson!) of Sullivan et al.
Overall, I think it wise to raise the level of discussion
of Sullivan et al from a "in passing remark" (Section 5.8)
in the section concerning population drift to one of
a more direct comparison of E(B-V) inferred from host class
versus SN colors.
One other point:
Section 1. Many theorists simply disagree with our conjecture
that SNe give the only "direct" indication of an acceleration.
I have argued endlessly with many (Kamionkowski, Steinhardt,
Lahav, Efstathiou..) who argue that the combination
of a low $\Omega_M$ from clusters, 2dF and lensing, combined with
a flat spatial curvature (CMB) inevitably leads to an acceleration
regardless of SNe.
I think it wise to add a reference to Efstathiou et al (2002) who combined
2dF and CMB to support the acceleration (as was done in Sullivan
et al I think).
regards
Richard
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