(it was send by e-mail on 26th of January and already discussed, but David told me to post it also here)
Nice paper, it reads quite smoothly, below some comments.
ABSTRACT:
12.27+2.75 −1.83 - too many significant digits (in general you have
somehow inconsistent number of significant digits, 1.58±0.32 but
2.0±0.1)
INTRODUCTION:
high-frequency BL Lac (HBL) ==> high-frequency peaked BL Lac (HBL)
Ansoldi ́c ==> Ansoldi
UV-optical an near infrared ==> UV-optical and near infrared
"For every event we calculated the image size
(number of photoelectrons) and the angular distance θ between
the source position and the reconstructed γ-ray arrival direction.
The arrival direction was estimated combining the information
from each telescope using the Disp method (Fomin et al. 1994;
Zanin et al. 2013). The separation between gamma and hadronic
events was performed using a random forest algorithm (Albert
et al. 2008). Energy look-up tables generated with Monte Carlo
simulations were used to estimate the energy of each event." - This is
just the standard analysis, expalined in MARS paper or in the upgrade
paper, I think you can safely skip it.
FIG1:
the blue dotted line ==> the red dotted line (?)
SECTION 3:
even while one can see it later in plots, when you give the deabsorbed
fit results you can specify immediately fit probability (as you did
for the observed one)
Also for each night the correlation energy was computed. - I think you
can skip this sentence. You do not plot this correlation energy
anywhere (and it also does not have any deaper physical meaning for
the source, because it depends on the observations), and even if you
normalize each spectrum at each own correlation energy for a PWL
spectrum this should not change the error of the spectral slope.
FIG3:
"The red line represents the fit to a simple line" - "... to a constant value"
"If the night of February 8th (third point from the left) is not
included in the fit, the probability is almos 50%.' - remove, there is
no apriori reason to remove this night, and it seems to me that is
simply has the smallest error and therefore all the small effects
(systematic or source intrinsic) will be mostly visible on it. If you
decide to keep the sentence after all, correct almos==>almost
There is also an alternative way to check if the source was varying.
You can plot the hardness ratio, F(E2<E<E3) / F(E1<E<E2) and see if it
is stable.
The problem is however that you have a broad zenith range, so you
could have a problem finding E1 which is working for all the nights.
Plus E2 is quite arbitrary.
SECTION4:
"the observed spectrum is determined" ==> "the observed spectrum is formed"
"A population of electrons are" ==> "A population of electrons is"
FIG 4:
did you try if it does not look better in log scale ?
otherwise you can clip the plot at 1.6 or something, because either
way one cannot see anything above this value.
I would suggest you to join Fig 4 and Fig 5 as two panels in one
figure, write also the EBL model in the figure caption.
SECTION5:
writing that cut-off energy can only be possitive is probably too
much: the energy cannot be negative, and nominallly putting it with
minus would result in pile-up spectral shape not a cut-off spectral
shape.
specrum ==> spectrum
SECTION5:
"the one has" ==> "the one that has"
To be honest I'm a bit lost how you estimated those systematic errors
in the end.
Have you used only the LP profile ?
For each scale i you should have alpha_i + d1alpha_i - d2alpha_i. From
the text it seems to ma that you have taken as the systematic error
(+d1alpha_syst-d2alpha_syst): d1alpha_syst = max (d1alpha_i) and
d2alpha_syst=max(d2alpha_i), independent plus and minus. It seems more
natural to take the spread of alpha_i.
Maybe a plot of alpha +/- dalpha vs energy scale would be useful here
(unless we are too scared to show it
).
If I were a nasty referee I would have asked if the claimed systematic
error of +/-0.15 in the spectral index (and maybe even more the
systematic error that Roberta gave on the curvature term in the recent
Crab paper) can lead to any additional systematic error.
SECTION6:
You should write (maybe even before) that 'E_gamma' (before called
'E') is measured in the observers frame
shouldn't (1+z)^2 be rather at E_max (i.e. broader range) ?
FIG8: are HESS and Fermi EBL results also in this plot ?
(it was send by e-mail on 26th of January and already discussed, but David told me to post it also here)
Nice paper, it reads quite smoothly, below some comments.
ABSTRACT:
12.27+2.75 −1.83 - too many significant digits (in general you have
somehow inconsistent number of significant digits, 1.58±0.32 but
2.0±0.1)
INTRODUCTION:
high-frequency BL Lac (HBL) ==> high-frequency peaked BL Lac (HBL)
Ansoldi ́c ==> Ansoldi
UV-optical an near infrared ==> UV-optical and near infrared
"For every event we calculated the image size
(number of photoelectrons) and the angular distance θ between
the source position and the reconstructed γ-ray arrival direction.
The arrival direction was estimated combining the information
from each telescope using the Disp method (Fomin et al. 1994;
Zanin et al. 2013). The separation between gamma and hadronic
events was performed using a random forest algorithm (Albert
et al. 2008). Energy look-up tables generated with Monte Carlo
simulations were used to estimate the energy of each event." - This is
just the standard analysis, expalined in MARS paper or in the upgrade
paper, I think you can safely skip it.
FIG1:
the blue dotted line ==> the red dotted line (?)
SECTION 3:
even while one can see it later in plots, when you give the deabsorbed
fit results you can specify immediately fit probability (as you did
for the observed one)
Also for each night the correlation energy was computed. - I think you
can skip this sentence. You do not plot this correlation energy
anywhere (and it also does not have any deaper physical meaning for
the source, because it depends on the observations), and even if you
normalize each spectrum at each own correlation energy for a PWL
spectrum this should not change the error of the spectral slope.
FIG3:
"The red line represents the fit to a simple line" - "... to a constant value"
"If the night of February 8th (third point from the left) is not
included in the fit, the probability is almos 50%.' - remove, there is
no apriori reason to remove this night, and it seems to me that is
simply has the smallest error and therefore all the small effects
(systematic or source intrinsic) will be mostly visible on it. If you
decide to keep the sentence after all, correct almos==>almost
There is also an alternative way to check if the source was varying.
You can plot the hardness ratio, F(E2<E<E3) / F(E1<E<E2) and see if it
is stable.
The problem is however that you have a broad zenith range, so you
could have a problem finding E1 which is working for all the nights.
Plus E2 is quite arbitrary.
SECTION4:
"the observed spectrum is determined" ==> "the observed spectrum is formed"
"A population of electrons are" ==> "A population of electrons is"
FIG 4:
did you try if it does not look better in log scale ?
otherwise you can clip the plot at 1.6 or something, because either
way one cannot see anything above this value.
I would suggest you to join Fig 4 and Fig 5 as two panels in one
figure, write also the EBL model in the figure caption.
SECTION5:
writing that cut-off energy can only be possitive is probably too
much: the energy cannot be negative, and nominallly putting it with
minus would result in pile-up spectral shape not a cut-off spectral
shape.
specrum ==> spectrum
SECTION5:
"the one has" ==> "the one that has"
To be honest I'm a bit lost how you estimated those systematic errors
in the end.
Have you used only the LP profile ?
For each scale i you should have alpha_i + d1alpha_i - d2alpha_i. From
the text it seems to ma that you have taken as the systematic error
(+d1alpha_syst-d2alpha_syst): d1alpha_syst = max (d1alpha_i) and
d2alpha_syst=max(d2alpha_i), independent plus and minus. It seems more
natural to take the spread of alpha_i.
Maybe a plot of alpha +/- dalpha vs energy scale would be useful here
(unless we are too scared to show it ;) ).
If I were a nasty referee I would have asked if the claimed systematic
error of +/-0.15 in the spectral index (and maybe even more the
systematic error that Roberta gave on the curvature term in the recent
Crab paper) can lead to any additional systematic error.
SECTION6:
You should write (maybe even before) that 'E_gamma' (before called
'E') is measured in the observers frame
shouldn't (1+z)^2 be rather at E_max (i.e. broader range) ?
FIG8: are HESS and Fermi EBL results also in this plot ?
