From: Chris Lidman (clidman@eso.org)
Date: Wed Aug 04 2004 - 11:11:32 PDT
Hi Serena,
Thank you for the most recent version of the paper. I have read it and
I provide some comments/suggestions below.
The ISAAC data are from ESO program 265.D-5721. This should appear as a
footnote to the title.
We use private communications in two parts of the paper. Before
submitting the paper, I would suggest that you contact both Schmidt and
Tonry to make sure that they are satisfied in the way we have used the
information they have provided us.
Section 3
=========
In the final paragraph of section 3, there seems to be some missing text
"... by the A similar ..."
Section 4.1
===========
In the last paragraph of section 4.1, you discuss the K-correction from
J and I. At one point, you add the phrase "and the 2MASS filter
definition". It is not clear to me what you mean here.
Also K_IJ is the K-correction from J to I and not Js to I.
Note that, for Vega, we have defined Js=J.
In the previous paragraph we define an ISAAC Js system (we correct the
standard star magnitude). This correction is derived by using the
Persson J-band filter curve, the Js filter, the Vega spectrum and a
spectrum of the standard (G-dwarf). In defining the ISAAC Js system, we
assume Js=J for Vega.
You quote an error of 0.05 magnitudes in the k-correction. Perhaps it
would be worth adding a sentence explaining where this error comes from.
This will be important, as you found a difference of up to 0.15
magnitudes for 99Q.
Section 4.2 and 4.3
====================
How do the stretch values compare with the Delta m15 measurements of
these two SNe. Are they consistent?
Section 5.
==========
The large scatter in the z~0.5 SNe is mostly due to 99Q and this should
be emphasised.
In the second last paragraph, you mention the "General problem regarding
J-band observations". I do not believe this to be true. For example
- The ZPs have an uncertainty of 0.01 magnitudes. This is very good.
- The Js filter curve is precisely known (I measured it myself with the
ISAAC spectrograph).
- The relationship between optical and IR systems is known to within
0.02 magnitudes.
I think that this paragraph should be deleted.
Section 6
=========
I think that you are too pessimistic about the result you derive on grey
dust. I would not say that the statistical significance of the results
are limited. Perhaps you can rephrase this in the following way
"Although these simple grey dust models are disfavoured by the data, the
number of SNe in the sample is small. In order to increase the
statistical significance of the result and to search for possible
systematic errors a larger sample is required."
In the second last paragraph, you say that one would need 20 z~0.5 SNe
to exclude grey dust at the 95% confidence level. You should mention
which model you are excluding here, because, in the previous paragraph,
you were able to exclude one model with 97% confidence.
I found some paragraphs in this section difficult to follow.
Cheers, Chris.
-- European Southern Observatory Alonso de Córdova 3107, Vitacura Casilla 19001, Santiago 19 CHILEPh. +56 2 463 3106 FAX +56 2 463 3101
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