From: Chris Lidman (clidman@eso.org)
Date: Sun Feb 19 2006 - 14:39:32 PST
Hi Gabriele,
Thanks for the revised version. Most of my suggestions now consist of
minor tweaks to help improve the clarity of the paper.
I am sure that I have missed some things, especially since I've
just returned from a long shift on Paranal and I am rather
tired. After you have read my comments, I suggest that you give the
paper to someone in the collaboration who can carefully read the
paper.
I do not think that you should add new SNe to this paper. On this
point,
we agree. Once this paper is done, what are your plans? Are you thinking
on working on the SNLS data set? This was the thrust of my question
in my earlier e-mail.
Regards,
Chris.
Abstract
========
You make the following comment on the revised abstract,
"In this way we are not mentioning at all the results of the EW for the
low z. I know is not the main point of the paper but I wonder if it
wouldn't be good to put it in the abstract for making the article
more appealing."
Yes, you are right. Here is another version, which could
probably still use some tweaking."
"We develop a method to measure the strength of the strongest
absorption features in Type SNe Ia spectra and use it to make a
quantitative comparison between the spectra of Type Ia supernova at
low and high redshifts. Through the strength of these features and
through measurements of the Ca II H and K velocity we show that the
spectra of a high redshift sample, consisting of 12 SNe Ia with
redshifts ranging from 0.212 to 0.912, are quantitatively similar to
the spectra of a low redshift sample. One supernova in our
high redshift sample, SN 2002fd at z=0.279, is found to have spectral
characteristics that are associated with peculiar 91T/99aa-like
supernovae."
A general comment
=================
In many places of the paper you use the acronym EW. This is OK, but it
can lead to clumsy word constructions in some cases. I take the the
first line in the caption of Fig. 4 as an example. Which do you think
is better,
"Measured EW values corresponding to ..."
or
"Equivalent width of the Fe II 4800 feature as a function of phase."
Sometimes, it is better to spell out the acronym. This was one example.
There are others.
Section 1
=========
4th paragraph
The Balland et al. paper (A&A, 445, 397) is now out. We should add this
article
to the list of references in the last sentence.
Section 2.1
===========
2nd paragraph
"... over luminous object" -> "... over-luminous objects"
Rephrase the sentence that starts with "Therefore, we consider ..." to
"The additional scatter that would be introduced by using data with
lower
signal-to-noise ratios would obfuscate the result"
or something similar.
3rd paragraph
"... error spectrum. It was ..." -> "... error spectrum, which was ..."
4th paragraph
"The estimated galaxy contamination, ..." -> "The contribution of the
galaxy
light, ..."
Figure 1 is a good start. One of the things we need to be aware of, is
that non-experts may think that the SNe spectra in this figure are
poor when the opposite is true. It is important that we do not create
a negative impression with this figure. Here are some suggestions to
make it better.
- For SNe with z > 0.4, put the label on the right. This will reduce the
amount white space that is in the figure.
- Make the SN labels larger
- Remove the word epoch, put the epoch in brackets and add a note in the
text explaining what the number in brackets means.
- Mark the regions that are used in the EW analysis. See Balland
et al. for an example.
- Try smoothing the data with a Savitsky-Golay filter. See Balland et
al.
Section 2.3
===========
1st paragraph
Maybe it is worth explaining what 91Taa means when it is first
used. E.g. you could say, "(We follow the convention of Li et al. when
describing 91T/99aa-like SNe by using 99Taa to represent this SN
subtype.)."
Rephrase
"The Ca II H&K feature ... SN 1991T like SNe."
to read
"The Ca II H&K feature in SN 2002fd is more prominent than the Ca II
H&K feature in SN 1991T, but less prominent than the Ca II
H&K feature in normal SNe Ia, such as SN 1994D."
or
"The strength of the Ca II H&K feature in SN 2002fd is between
that of 91Taa-like and normal SNe."
Table 1.
The font for footnotes "a" through "d" in the table is different to
the font used below the table. Same comment applies to Table 2.
Replace
"that could affect the cosmological measurements".
with
", which might affect the derivation of cosmological parameters
from SNe Ia."
Section 3
=========
1st paragraph
"phase" -> "phase,"
"distribution properties" -> "distributions,"
"see for a review Filippenko (1997)" -> "see Filippenko (1997) for a
review"
"case" -> "cases"
"severe" -> "dramatic"
"and Type Ia subtypes have been identified to account for a
morphological classification"
->
"resulting in the definition of SNe Ia sub-types."
"dishomogeneities" -> "dissimilarities"
"my means" -> "by means"
2nd paragraph
"compare" -> "comparing"
"In the following section EW is defined and the properties are ...
discussed"
->
"In the following sections, we describe how we measure the EW of the
broad absorption features in SN Ia spectra and we apply it to a sample
of nearby SNe Ia."
I suggest that you delete the last three sentences in this paragraph,
unless
you are sure that Gaston will publish his paper.
Section 3.1
===========
The first and second paragraph needs some rewording.
2nd paragraph
"i.e." -> "because of"
3rd paragraph
"As already mentioned" -> "As already mentioned,"
In the footnote 3 on the bottom of page 6.
"and the possible" -> "with the possible"
In the last paragraph you can say "By definition, the rest frame EW ..."
and you can then delete the parenthetical remark.
Section 3.2
===========
In the spirit of the titles you have used for sections 3.1 and 3.2, I
would
suggest the abbreviated title - "Measurement technique"
1st paragraph
"Measuring EW ..." -> "Measuring the EW ..."
"since the identification of the local maxima bounding ... visually."
->
"since the local maxima bounding an absorption feature can be identified
easily."
"poor quality spectra" -> "low signal-to-noise data" I prefer this
because the
high redshift data are not poor quality data.
"complex" -> "difficult"
Delete the word practical
"which minimize" -> "that minimizes"
In the list of items on page 7.
"on Eqn. 1" -> "in Eqn. 1"
"To the data, ..." -> "A straight line is fitted to the data in the
fitting
regions"
2nd paragraph
"Larger wavelength span would ..." -> "Larger wavelength spans would
..."
Section 3.3
===========
Last paragraph
"presents photometric" -> "has photometric"
"which make" -> "that make"
Section 3.4
===========
Last paragraph
"The decrease of EW ..." -> "The decrease in the EW ..."
Delete "by giving the relative decrease ... types."
You can then adjust the title of Table 6 to read
"The fractional decrease in the EW corresponding to a 10% increase in
the
amount of contamination from the host."
Replace
"Since the SNe ... on that end"
with
"Since SNe Ia near maximum light are generally bluer than their hosts,
errors in estimating the amount of host galaxy contamination
leads the larger EW errors for features at redder wavelengths."
Section 3.5
===========
1st paragraph
The first sentence is not necessary. The second is sufficient.
Section 3.5.1
=============
1st paragraph
"The values of the EW increase constantly ..." -> "The EW increases ..."
3rd paragraph.
The paragraphs starts with "This", which might confuse the
reader. Perhaps, the new paragraph should start with the 2nd last
sentence of the 2nd paragraph, i.e. the one that starts with "The
different sub-types ..."
\delta is used in the text, \Sigma in the table. Actually, in this case
\delta is more appropriate for columns 6 and 8. I'm sorry if I have
changed my mind on this point.
\delta is in the footnote. The footnote appears on the page before the
table.
Section 3.5.2
=============
3rd paragraph.
"Other SN subtype ..." -> "Other SN subtypes ..."
Section 4
=========
in point 2
"equivalent width measurements" -> "the equivalent widths"
Section 4.1.1
=============
1st paragraph
"would tend to" -> "might"
3rd paragraph
"data quality range found in our data set" -> "signal-to-noise ratios
in the
data,"
"estime" -> "estimate"
The biggest weakness of the technique we use to estimate the amount of
host galaxy subtraction is that we use a fixed number of galaxy
templates.
In real data, host galaxy SEDs will be more varied, so the estimate in
how accurate we can remove the flux of the host galaxy is probably
an underestimate.
Section 4.1.2
=============
1st paragraph.
"Figs. 9 and 8" -> "Figs. 8 and 9"
EW's indicates possession, which is not the case here. Use EWS.
Personally,
I find the acronym EWS rather ugly. It might look nicer if you spell
out the acronym. Also "measured EW values" is better written "equivalent
widths".
The semi-colon after "parenthesis" should be a full stop.
"possible fitting regions uncertainties" -> "possible fitting region
uncertainties"
5th paragraph
"Fig. 10 show" -> "Fig. 10 shows" and a full stop at the end of the
sentence.
"low-redshift normal and under-luminous" -> normal and under-luminous
low-reshift"
Last paragraph.
"lower metallicity progenitor" -> "lower metallicity progenitors"
The other possibility, of course, is that the Lentz models are wrong.
Table 10.
The first sentence is messy. Try
A statistical comparison of the equivalent widths of high-redshift SNe
with the equivalent widths of normal and under-luminous low-redshift
SNe.
If it is possible, replace the word "faint" with the word
"under-luminous",
so that it is clear that the faint and under-luminous SNe are the same.
Section 5
=========
1st paragraph
"We also find based on spectral properties alone that, .." -> "We also
find, based on spectral properties alone, that ..."
3rd paragraph
"EWof" -> "EW of" (occurs twice)
Last paragraph.
"difference in" -> "differences between"
"has" -> "has been" in the last sentence
I feel that something is lacking in this paragraph.
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