From: Gabriele Garavini (garavini@in2p3.fr)
Date: Tue Mar 08 2005 - 00:13:03 PST
Hi Chris,
I'm sorry, I put the wrong link. Now the latest version (2.4) is
available.
Cheers
Gabriele
On Mar 8, 2005, at 12:38 AM, Chris Lidman wrote:
> Hi Gabrielle,
> Could you check that the version that is on the web is the
> latest one. The latest version that I could find is
> version 2.0 from Feb 21st.
>
> Cheers, Chirs.
>
> On Fri, 2005-03-04 at 14:09, Gabriele Garavini wrote:
>> Dear Chris, Dear All,
>>
>> I've implemented the latest comments from Chris, Andy and Rob into a
>> new draft of the paper and made some more modifications
>> (supernovae.in2p3.fr/~garavini/papers)
>>
>>
>> The most relevant news are:
>>
>> Section 3.3
>>
>> I've completely redone the statistics. I've included in the chi^2
>> test
>> also the error on the x axis into. It was not there before. This was
>> done propagating it into an y axis error according to the ew model of
>> the low redshift SNe. This needed to be done for correctness, and has
>> some nice consequences especially for MgII. Since the ew evolution of
>> this feature has a big derivative wrt time the difference in the
>> probability in table 5 is significant. Now the hypothesis that low and
>> high redshift SN have the same ew trend is true for both Fe and Mg.
>> Also, I've included in table 5 the same chi^2 test considering in the
>> uncertainties also the systematic due to the misidentification of the
>> fitting regions.
>>
>>
>> Section 3.2.2
>>
>> The last paragraph about the systematic due to host galaxy removal was
>> not exhaustive. I've expanded it explaining in some more details where
>> the 10% of uncertainty comes from.
>>
>>
>> Section 3.2.3
>>
>> In the second last paragraph of page 8 we commented on the higher
>> than average values of ew for Mg before max light (a 2-sigma effect).
>> The previous version of the paper included an explanation that did not
>> convince neither me nor Chris. So I've done some thinking and some
>> checks. Looking at the spectra and trying to identify the feature I
>> noticed that in the early epochs since this feature is shallow it is
>> easy to misidentify the maxima perhaps including some of the neighbor
>> absorptions. This would bias the ew measurements toward higher values.
>> This effect is taken into account by the misidentification systematic
>> uncertainties. In the current version of this paragraph I explain that
>> this could be the origin of the problem but that anyway it is not
>> statistical significant.
>>
>>
>> Section 3.2.1
>>
>> I included the latest comments from Rob. We now agreed on a
>> description
>> that hopefully will allow the reader to measure ew as was done for
>> this
>> paper.
>>
>>
>> This should cover all the comment and worries raised so far.
>>
>> Please let me know what you think and how we proceed from here?
>> I think now the paper can safely state that we do not see evolution.
>> The new version includes all the authors that were included into the
>> VLT paper. I know some of the affiliation are wrong. I'll check them
>> out.
>>
>>
>> Thank you very much
>> Cheers
>> Gabriele
>>
>>
>>
>> On Feb 23, 2005, at 4:48 PM, Chris Lidman wrote:
>>
>>> Hi Gabriele,
>>> I've given some more thought about the possibility of doing a 2D KS
>>> test with the data in figure 5. It seems to me that we cannot do
>>> this test because one is not sampling the nearby and
>>> distant samples randomly.
>>>
>>> The alternative is the chi-sq test, as you have done. The
>>> resulting probability (0.15) is low. The question we must now ask
>>> ourselves is do we believe this result. If we do, then we cannot
>>> say that there is no evidence for evolution, as we do in the
>>> abstract.
>>>
>>> There could be reasons for the difference. The example you give
>>> is systematic errors in host galaxy subtraction. If this is the case,
>>> why would if affect the the Mg II index but not the FeII index.
>>>
>>> Regards, Chris.
>>>
>>> On Tue, 2005-02-22 at 20:56, Chris Lidman wrote:
>>>> Hi Gabriele,
>>>> Thanks for the reply. I forwarded your paper to Andy and he has
>>>> provided some additional comments. Andy's comments consist of
>>>> grammatical corrections, which I reproduce below, and an important
>>>> question regarding host galaxy subtraction.
>>>>
>>>> Before I list Andy's comments, I'd like to add to my point
>>>> concerning
>>>> the significance of the difference seen in figure 5.
>>>>
>>>> The test you have done is to test whether high redshift SNe are
>>>> more
>>>> similar to low redshift normal SNe or to low redshift underluminous
>>>> SNe.
>>>> You have found the former to be true. However, this does not mean
>>>> that
>>>> they are the same as low redshift normal supernova. Hence, you
>>>> cannot
>>>> conclude that there is no evolution. For this, you need to conduct a
>>>> more sophisticated test.
>>>>
>>>> It may not be easy to do this in 2 dimensions. In 1D, the
>>>> obvious tests would be the KS test and Student's t-test.
>>>> However, using a web search, I found the following web page
>>>> which describes a 2D KS test.
>>>>
>>>> http://beowulf.lcs.mit.edu/18.337-2002/projects-2002/ianchan/KS2D/
>>>> Project%20Page.html
>>>>
>>>> Have a look and let me know what you think.
>>>>
>>>> In addition to Andy's comment regarding host galaxy subtraction,
>>>> one
>>>> should note that the bias could go either way. In some cases, you
>>>> might
>>>> subtract too much host and in other cases you might subtract too
>>>> little.
>>>> Currently, the paper assumes that the error in the subtraction is
>>>> 10%.
>>>> Where does this percentage come from? I think that this needs more
>>>> justification.
>>>>
>>>> Cheers, Chris.
>>>>
>>>> Start of Andy's comments
>>>> ========================
>>>>
>>>> Comment #1
>>>>
>>>> The largest source of uncertainty is the host galaxy subtraction.
>>>> Yet
>>>> this is swept under the rug. If this was done using the
>>>> determination
>>>> from my program, for example, you can't trust any of the conclusions
>>>> from the paper. My program simultaneously fits host galaxy and SN
>>>> templates. In other words, it *assumes* that the high-z spectra is
>>>> similar to a low-z one and subtracts an amount of host light such
>>>> that
>>>> the high-z and low-z spectra will look similar. The proper thing to
>>>> do
>>>> would be to use the photometry (e.g. percent increase) to constrain
>>>> the
>>>> amount of host galaxy light, and to use imaging and spectral
>>>> features
>>>> to
>>>> constrain the host characteristics. You might be able to say some
>>>> spectrum has 30% host +/- 10%, and is either an E, SO, or Sa. Then
>>>> you
>>>> could do different subtractions in that parameter space and test the
>>>> results. Defining a technique like this would be a great addition
>>>> to
>>>> this paper because any time people use high-z spectra they are going
>>>> to
>>>> have to do something like this.
>>>>
>>>> Comment #2
>>>> ==========
>>>>
>>>> One other point -- in the SNLS we have many 91T/99aa SNe at high
>>>> redshift. So there is no need to make a big deal out of having one
>>>> in
>>>> the sample, as this paper does.
>>>>
>>>> Minor comments
>>>> ==============
>>>>
>>>> p. 1
>>>> Intro, par. 1 -- plural of supernova is supernovae
>>>> tidly ????
>>>> par. 4 it should be pointed out that the effect metallicity has
>>>> on the spectrum pointed out by Hoeflich and Lentz are only for
>>>> early-time
>>>> spectra, of which there aren't many here.
>>>>
>>>> par. 6 -- I have submitted a paper on SNLS gemini spectra -- Howell
>>>> et
>>>> al.
>>>> 2005, ApJ, submitted
>>>>
>>>> p. 2, section 2.1 last sentence, One SNe -> One supernova
>>>>
>>>> last paragraph of section -- two days is no longer the uncertainty
>>>> for
>>>> the
>>>> spectroscopic epoch determination in Hook et al.
>>>>
>>>> section 2.3, par 1 -- you say EWS but it is not defined yet.
>>>>
>>>> p. 4
>>>> table 2 'Si' should be 'Si 4000' since you say it is absent in
>>>> underluminous SNe.
>>>>
>>>> first paragraph on page - there is a period missing before SN 2002fd
>>>>
>>>> p. 5
>>>> 3.1, 3rd par. "uncertainty in the redshifts is taken to be 300 km/s
>>>> if
>>>> the
>>>> redshift was estimated from galaxy lines..."
>>>> shouldn't this be proportional to the redshift?
>>>>
>>>> 3.2 first sentence -- delete ", they" and second comma.
>>>>
>>>> p. 6
>>>> "possible involved" delete involved
>>>>
>>>> p. 7 last par in 3.2.1 delete space in "spectra ,"
>>>>
>>>> 3.2.3, 4th par -- delete space: "( with"
>>>>
>>>> p. 8 3.3 miss-identification -> misidentification
>>>> this whole parenthetical expression should be made into a new
>>>> sentence
>>>> because it is confusing with "uncertainties" written twice in a row.
>>>>
>>>>
>>>>
>>>> On Tue, 2005-02-22 at 05:24, Gabriele Garavini wrote:
>>>>> I'm very sorry chris I sent by mistake the wrong file.
>>>>> Here is the one I meant to send.
>>>>> Thanks
>>>>> Gabriele
>>>>>
>>>>> On Mon, 21 Feb 2005, Chris Lidman wrote:
>>>>>
>>>>>> Hi Gabriele,
>>>>>> Could you resend the attachment. The one I received seems to be
>>>>>> chopped at the end.
>>>>>>
>>>>>> Regards,
>>>>>>
>>>>>> Chris.
>>>>>>
>>>>>> On Mon, 2005-02-21 at 13:29, Gabriele Garavini wrote:
>>>>>>> Dear Chris
>>>>>>>
>>>>>>> thanks you very much for the careful reading of the paper. I've
>>>>>>> implements most of you comments. Please find all my answers in
>>>>>>> the
>>>>>>> attached file. I also changed extensively the section about EW
>>>>>>> (3.2) I
>>>>>>> hope this will allow us to go to submission shortly.
>>>>>>>
>>>>>>> Thanks again
>>>>>>> Hasta la vista.
>>>>>>> Cheers
>>>>>>> Gabriele
>>>>>>
>>>>>>
>>>>>>
>>>>
>>>>
>>>
>>>
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