From: Andy Howell (DAHowell@lbl.gov)
Date: Wed Feb 26 2003 - 15:11:10 PST
Good job Rob -- you have done a lot of work, and I think this will be a
very interesting paper.
Substantive comments first:
1. Someone made the comment that we should say that in all cases the SN
and galaxy redshift agree.
This may not be true. For 9819/SN1998ba the galaxy redshift was
z=0.393, but the redshift of the SN (and the one used int the paper is
0.43). This is the one you threw out for being the wrong color. Did
you try doing a K-correction for z=0.393 to see what the difference is
(although this almost certainly is not the redshift of the SN)?
Here is the nearby galaxy's spectrum, showing its redshift:
http://panisse.lbl.gov/collab/data/spec/homesp/eso_mar98/reduc_tel/9819_galz.ps
Here is the SN at that redshift (it doesn't fit well):
http://panisse.lbl.gov/collab/data/spec/homesp/eso_mar98/reduc_tel/9819_snz.ps
Here is the SN at z=0.43:
http://panisse.lbl.gov/collab/data/spec/homesp/eso_mar98/reduc_tel/9819_snz2.ps
It is possible that the galaxy at z=0.393 is in the foreground and is
causing the extinction seen for that SN. You can see Robert Quimby's
host info on it here:
file:///home/lilys/quimby/hosts/html/9819.html
He writes: "Small round host with overlaping companion (which is the
host?)."
On the other hand, the reduction notes Isobel wrote say: "The Sn is at
550 and the nearby galaxy is at 565. The redshift of the nearby galaxy
is 0.39." If those are pixels, then the redshift she is quoting is
probably for the brighter galaxy to the upper right in the image on
Quimby's page. This is probably not the host.
I apologize if this has all been covered before -- this happened before
I joined the group. I don't have the 2d spectra to check.
2. You don't say anything about the spectroscopic IDs of any of these
SNe. Non-Ia contamination is a very important issue, but I think we are
on solid ground with these 11 SNe. All were identified as Ia's in the
circulars. From a quick look at the spectra I would say that 8 are
certain Ia's, and the other 3 are probable one Ia's (but there is no Si
to be absolutely definitive). When you consider the colors and light
curves this means that all of the new SNe in this paper pretty positive
Ia's. Of course the same cannot be said of the original 42 SNe. I
still want to see a fit removing the SNe that we aren't sure are Ia's
from the 42, but I suppose that is never going to happen.
3. P99 commented that the results still hold if stretch is ignored. Is
this still true?
4. You say that these results are better because of the colors at least
5 times in the paper, often followed by something like "but the old
results were still ok!" This gets redundant.
Ok, here are the more minor issues. I have not repeated comments I
remembered that others have already made, but I'm sure there are still
some duplications.
Everywhere that you have a sn year such as 1998ba you should put "SN" on
the front (SN 1998ba). I'm pretty sure the journal will make you do this.
Abstract: I agree with Isobel that we should start off strong with our
results, not with history in the abstract. Banishing the first few
sentences to the introduction will fix my next problem, that the second
sentence of the introduction is confusing and should be reworded. While
you are at it, replace "extremely high confidence" with something
quantitative.
p. 2, last full sentence on the page:
"With these advantages, the precision of the lightcurve measurements is
so much greater for the 11 supernovae in this paper than was the case
with the 42 SNe of P99 that even though there are only 1/4 as many
objects, just these 11 high-redshifte supernovae provide limits on the
cosmological parameters comparable to limits from the previous work."
Holy extraneous modifying clauses, Batman! I suggest: "Even though
there are only 1/4 as many objects, the precision of the new lightcurves
presented in this paper is so great that the limits placed on the
cosmological parametes are comparable to previous work."
p. 4, "z is only precise to typically" Omit only.
p. 5 For Table 1, all of the z's are given to 3 significant digits,
even where we only have the redshift from the SN. We should label the
SN-only redshifts.
p.6 Section 2.2 first paragraph "then" should be "the" before "WIYN
3.5M", and this should be "3.5m".
Also, was it Keck I or Keck II?
p.6 Last sentence: "For low-redshift supernovae, so as to match as
closely...": two modifying clauses before you even get to the subject
of the sentence is too much.
p.7 beginning of last paragraph on page. "For most of the supernovae,
the zero offset of the lightcurve was fixed at zero...." I know what
you mean, but you might want to explain what a "zero offset" is.
p. 9 section 2.3 first paragraph. "The WFPC2 filters are enough
different from the ground-based filters, however, that a linear term is
not sufficient, and moreover ..." However and moreover in the same
sentence is too much. Split into two sentences. And change to
"different enough".
p. 9 last par. Put in dashes or parentheses to clarify, e.g. "For each
color -- B-V, V-R, and R-I -- every data point ..."
p. 13, first paragraph -- I agree that a graphic would help explaining
the ridge-line process.
p. 14 last par. Can cut out redundant info in first sentence so it
becomes, "The greatest improvement this paper shows over the previous
high-redshift supernova data is that the R-I colors have been measured
to much higher precision."
p. 15 First sentence-- "From this, P99 argued that, omitting two
obviously reddened supernovae to create their "case C" subset, the high
redshift supernovae did not show significant host galaxy reddening
relative to the low redshift supernovae." Middle clause is distracting
and makes the sentence unclear. Change to something like, "From this,
P99 argued that in their Case C subset the high redshift..."
p. 17 last par. Sentence that begins "Whereas modest..." should be split
into two sentences.
p. 18 For the sentence that begins "The range of parameter space
explored was...", another way to write it is omega_m = (0,3),
omega_l=(-1,3)." That is, assuming that you don't mean [0,3] (was zero
allowed?). Also, make sure you get the number of parentheses right --
they aren't right at the moment.
p. 19 Somewhere where you explain stretch, we should also reference
Phillips 1993 for establishing the light curve-decline relationship.
p. 21 last paragraph -- "Figures 3" should be Figure 3., and the
sentence that begins "If the supernovae at higher redshifts..." is unclear.
p.23, 24 % sign left off (probably forgot the \)
p.25 3rd line "effects" should be "affects"
p.25 Last sentence, "Because there are only two parameters..." sentence
is unclear. 3(!) clauses before you get to the subject.
p. 27 end of 1st par. "...the energy density of the universe must not
be normal matter, i.e. a cosmological constant or dark energy." This
sounds like you mean that a cosmological constant is normal matter.
Also, a cosmological constant is dark energy -- I think you mean
quintessence.
p. 27 Section 4 only has one subheading, 4.1. This is not allowed.
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