M 1–92 Revisited: New Findings and Open Questions: New NOEMA Observations of Minkowski’s Footprint
, Marcelino Agúndez 2, Valentín Bujarrabal 3, Arancha Castro-Carrizo 4, Jean-François Desmurs 1, John-Eduard Martínez-Fernández 1,5,6, Carmen Sánchez Contreras 7 and Miguel Santander-García 1Round 1
Reviewer 1 Report
The authors have revisited M1-92 object performing new observations. The maps shown in the paper provide new insights. They find molecular species in the ionized regions of the nebula, the structure of the massive equatorial component, and the presence of winds interaction. Also, the AGB evolution is terminated by a massive mass loss.
Minor revisions:
1- As the authors mention mass loss rate, they use M_O/a, as 'a' is the age. It should be clarified why you use these units and not M_O/yr.
2- More citations on bipolar PNe must be mentioned in the introduction as there are many hydrodynamical works studied the physics behind this kind of PN.
Author Response
Original referee comments are in blue italic. Our reply to each point is given using black regular characters.
The authors have revisited M1-92 object performing new observations. The maps shown in the paper provide new insights. They find molecular species in the ionized regions of the nebula, the structure of the massive equatorial component, and the presence of winds interaction. Also, the AGB evolution is terminated by a massive mass loss.
Minor revisions:
1- As the authors mention mass loss rate, they use M_O/a, as 'a' is the age. It should be clarified why you use these units and not M_O/yr.
According to IAU recommendations as in "https://www.iau.org/publications/proceedings_rules/units/", the preferred abbreviation for the time unit year is "a" from the Latin term "annus" (see table 5 for non-SI units that are recognised for use in Astronomy). We prefer to follow IAU recommendations and use M_o/a for the mass loss in Solar masses per year rather than M_o/yr.
2- More citations on bipolar PNe must be mentioned in the introduction as there are many hydrodynamical works studied the physics behind this kind of PN.
Given the limited size of this contribution, and the fact that the introduction is focused exclusively on the case of M1-92, we believe that it is not appropriate here to give references of the many hydrodynamical works devoted to the physics behind this kind of PN. However, it is true that we have not mentioned this important aspect, therefore we have included the references for a couple of papers dealing with the modelling of this particular source.
Reviewer 2 Report
The authors observed molecular lines of the pPN M1-92. By calculating isotopes ratios they conclude that the AGB with initial mass of 1.7Msun underwent an event that terminated its evolution before getting the chance to become carbon rich. By measuring velocities in the nebula they derive a kinematic age for this event and suggest that this event is a huge mass loss event that occurred 1200 years ago. They also detect a warm clump in the center of the nebula.
I think this is a nice paper with good observational work and follow-up analysis. I recommend its publication and have the following suggestions to the authors:
End of Introduction: Can the authors explain what is the Momentum Excess Problem? I think even 2-3 sentences can suffice.
Section 2:
Can the authors mention which observatory/facility hosts the IRAM NOEMA mm-wave interferometer?
Section 2:
The authors made a calculation to de-project the nebulae, as shown in Figure 2. The results are very impressive. During this process the authors applied equatorial averaging. However earlier they mention that the (south-east) lobe is smaller. I think it would be also interesting to view the result before the averaging, emphasizing the differences between the lobes, and identifying individual knots. I think such a product can be useful for future modeling the finer details of this pPN.
Section 5 and Figure 4:
Can the authors emphasize that the derived velocities are projected values (if I understand correctly).
Discussion: I think it is worthy to mention that M 1- 92 has an extra extra kinetic energy, namely energy in the lobes above that of a regular AGB wind. This extra energy, they suggest was suggested to come from the post-AGB jets (Bujarrabal et al. 1998, ApJ, 504, 915). If the authors object to this suggestion they may of course explain their alternative opinion. Also, iIt was further suggested that it was created by an ILOT event (Soker & Kashi 2012, ApJ, 746,100 ). This is in agreement with the author's claim that the most plausible mechanism involves a binary. The authors may want to comment on that.
Minor:
Line 33: Correct the units to Msun year^{-1}.
Line 42, 51 and other places : 1200 years. Seems as every time "year" should appear "a" appears instead.
Line 66: Please define PDR.
Author Response
Original referee comments are in blue italic. Our reply to each point is given using black regular characters.
The authors observed molecular lines of the pPN M1-92. By calculating isotopes ratios they conclude that the AGB with initial mass of 1.7Msun underwent an event that terminated its evolution before getting the chance to become carbon rich. By measuring velocities in the nebula they derive a kinematic age for this event and suggest that this event is a huge mass loss event that occurred 1200 years ago. They also detect a warm clump in the center of the nebula.
I think this is a nice paper with good observational work and follow-up analysis. I recommend its publication and have the following suggestions to the authors:
End of Introduction: Can the authors explain what is the Momentum Excess Problem? I think even 2-3 sentences can suffice.
Done
Section 2:
Can the authors mention which observatory/facility hosts the IRAM NOEMA mm-wave interferometer?
As there is only one telescope at the site, the name NOEMA (NOrthern Extended Millimeter Array) is used both for the instrument (the array) and the observatory/facility. However, we have added the name of the geographical size.
Section 2:
The authors made a calculation to de-project the nebulae, as shown in Figure 2. The results are very impressive. During this process the authors applied equatorial averaging. However earlier they mention that the (south-east) lobe is smaller. I think it would be also interesting to view the result before the averaging, emphasizing the differences between the lobes, and identifying individual knots. I think such a product can be useful for future modeling the finer details of this pPN.
I think that there is a misunderstanding here. The southeast lobe appears fainter and somewhat less extended but only at optical wavelengths. This is the result of the obscuration due to the dense equatorial structure dividing the two lobes. This asymmetry is not present at radio wavelengths. In particular, in the CO emission, the differences between the SE and NW lobes are of the order of the noise in the maps. This is why we have decided to average the emission from both lobes to increase the S/N in the 3D-reconstruction. Due to this, we believe that it is not necessary to show the results before this equatorial mirror averaging as they are not relevant. We have rephrased the introduction to make it more clear that the lobe asymmetry is not intrinsic, and it is not present at radio wavelengths.
Section 5 and Figure 4:
Can the authors emphasize that the derived velocities are projected values (if I understand correctly).
Done
Discussion: I think it is worthy to mention that M 1- 92 has an extra extra kinetic energy, namely energy in the lobes above that of a regular AGB wind. This extra energy, they suggest was suggested to come from the post-AGB jets (Bujarrabal et al. 1998, ApJ, 504, 915). If the authors object to this suggestion they may of course explain their alternative opinion. Also, iIt was further suggested that it was created by an ILOT event (Soker & Kashi 2012, ApJ, 746,100 ). This is in agreement with the author's claim that the most plausible mechanism involves a binary. The authors may want to comment on that.
We have added a couple of sentences on this issue.
Minor:
Line 33: Correct the units to Msun year^{-1}.
According to IAU recommendations as in "https://www.iau.org/publications/proceedings_rules/units/", the preferred abbreviation for the time unit year is "a" from the Latin term "annus" (see table 5 for non-SI units that are recognised for use in Astronomy). We prefer to follow IAU recommendations and use M_o/a for the mass loss in Solar masses per year rather than M_o/yr.
Line 42, 51 and other places : 1200 years. Seems as every time "year" should appear "a" appears instead.
See answer above
Line 42, 51 and other places : 1200 years. Seems as every time "year" should appear "a" appears instead.
See answer before.
Line 66: Please define PDR.
We have removed the acronym as it was only used twice in the text.
Reviewer 3 Report
Please, describe the colour scales used in the images depicted in Figs. 1, 2 and 4.
line 70: Do you mean CO isotopologues (instead of isotopomers)?
Eq. (3): I think the third term contains a typo.
line 112: What is the uncertainty of this isotopic ratio?
line 114: The predictions for the C/O abundance ratio also depend on metallicity and on the model assumptions. A comparison with models from different authors might be of interest (please, remember to include the references for these works). A comment on this would improve the discussion, and it seems to be required for the part where the authors conclude that there is "strong evidence that the AGB evolution of the source was terminated prematurely".
lines 205-207: Please, provide more details to make this affirmation more clear.
In reference number 7, the year should be 1998.
Author Response
Original referee comments are in blue italic. Our reply to each point is given using black regular characters.
Please, describe the colour scales used in the images depicted in Figs. 1, 2 and 4.
Fig. 1 and leftmost panel in Fig. 4 are taken from [7] and are only plotted here to help in the comparison of the location of the different tracers (dust = reflected light, optical forbidden atomic lines, and molecular lines). We think that if the reader is interested in knowing about the intensity scale in these plots, it is better to have a look at the original paper, where there is plenty of information on these and other related issues (calibration, continuum subtraction, etc.). However, it is true that in Fig. 2 and the central and right panel in Fig. 4, the intensity scale is missing. Since in these latter cases both the contours and the colour scale represent the same magnitude, we have decided to indicate the intensity scale by giving the values for the plotted contours.
line 70: Do you mean CO isotopologues (instead of isotopomers)?
Corrected
Eq. (3): I think the third term contains a typo.
Done. Thanks for spotting this.
line 112: What is the uncertainty of this isotopic ratio?
Done. The isotopic ratio is 1.6+-0.15 which translates into an initial mass of 1.7+-0.10. Note that both C17O and C18O lines were measured simultaneously and that therefore their relative intensity is free from calibration errors. These errors have been included in the text.
line 114: The predictions for the C/O abundance ratio also depend on metallicity and on the model assumptions. A comparison with models from different authors might be of interest (please, remember to include the references for these works). A comment on this would improve the discussion, and it seems to be required for the part where the authors conclude that there is "strong evidence that the AGB evolution of the source was terminated prematurely".
Agree. The condition for C-rich at the end of the AGB depends on the metallicity. For our target, we reasonably expect solar-type metallicity, for which targets become C-rich between 1.5 and 3.5--4 solar masses. We have rephrased the sentence, stating that we assume a normal (solar) metallicity for M1-92 and a reference for the nucleosynthesis yields for AGB stars. Note that there are no measurements for the metallicity of M1-92 that we are aware of, but that for an intermediate-mass star at 2.5 kpc, we should not expect values far from solar (Pedichelli et al 2009).
lines 205-207: Please, provide more details to make this affirmation more clear.
In an AGB circumstellar envelope, the size of the emitting region of a particular species is controlled by the balance between the photodissociation rate of the species and the arrival of new molecules from inner layers as a result of the expansion of the envelope. Rare isotopologues of species tend to show less extent since their self-shielding is lower. In the case of M1-92, as 13CO, C17O and C18O show similar extents, this can not be the case, suggesting that the size of the molecular nebula is just a result of its self-similar growth. We have rephrased the sentence, hoping that it is clearer now.
In reference number 7, the year should be 1998.
Done
Reviewer 4 Report
This paper reports on NOEMA observations of a pre- (or proto-) planetary nebula, namely the M1-92 system, as well as reporting on some simple but effective modelling of the observations. The paper is worthy of publication. I have noted a small number of comments and some typos to tidy up.
Small points:
1) p.4 You mention the derived oxygen isotopic ratio of 1.6 and a derived initial mass of 1.7Msun. Is it possible to estimate any errors on both
quantities. These values paint a nice picture, but is it 1.7\pm
0.1Msun or \pm 1.0Msun?
2) p.6 Fractional abundances - are the quoted values correct
(otherwise can you specify the assumptions made).
The paper could use a small bit of language editing - some examples below:
Abstract: "this type of source.." not "sources"
Several places: You use "a" presumably for a~no (with the tilde - I know enough Spanish to know what it means without the accent). Presumably should be year or yr. (eg p.2 Msun a^-1, 1200 a etc).
p.3 You don't define PDR (you use the term photo-dissociation elsewhere but don't define PDR).
p.5 caption 16667MHz - missing MHz.
p.5 "observed transitions cover"- not "transition".
p.5 Should be "two or more" not "two o more"
p.6 Should be T_{ex} not Tex.
Author Response
Original referee comments are in blue italic. Our reply to each point is given using black regular characters.
This paper reports on NOEMA observations of a pre- (or proto-) planetary nebula, namely the M1-92 system, as well as reporting on some simple but effective modelling of the observations. The paper is worthy of publication. I have noted a small number of comments and some typos to tidy up.
Small points:
1) p.4 You mention the derived oxygen isotopic ratio of 1.6 and a derived initial mass of 1.7Msun. Is it possible to estimate any errors on both quantities. These values paint a nice picture, but is it 1.7\pm 0.1Msun or \pm 1.0Msun?
Done. The isotopic ratio is 1.6+-0.15 which translates into an initial mass of 1.7+-0.10. Note that both C17O and C18O lines were measured simultaneously and that therefore their relative intensity is free from calibration errors. These errors have been included in the text.
2) p.6 Fractional abundances - are the quoted values correct
(otherwise can you specify the assumptions made).
The rotational diagram formalism provides values for the column densities, that can be transformed into densities, for the studied species. From previous works, the density of molecular hydrogen in the same equatorial region was also estimated (see [2]). Since H2, is by far the most abundant molecular species, by dividing these two numbers we directly obtain the relative abundance of SO w.r.t. H2,or the total molecular content. We have rephrased the sentence to make it clearer.
The paper could use a small bit of language editing - some examples below:
Abstract: "this type of source.." not "sources"
Done
Several places: You use "a" presumably for a~no (with the tilde - I know enough Spanish to know what it means without the accent). Presumably should be year or yr. (eg p.2 Msun a^-1, 1200 a etc).
According to IAU recommendations as in "https://www.iau.org/publications/proceedings_rules/units/", the preferred abbreviation for the time unit year is "a" from the Latin term "annus" (see table 5 for non-SI units that are recognised for use in Astronomy). We prefer to follow IAU recommendations and use M_o/a for the mass loss in Solar masses per year rather than M_o/yr.
Line 42, 51 and other places : 1200 years. Seems as every time "year" should appear "a" appears instead.
See answer before.
p.3 You don't define PDR (you use the term photo-dissociation elsewhere but don't define PDR).
We have removed the acronym as it was only used twice in the text
p.5 caption 16667MHz - missing MHz.
Done
p.5 "observed transitions cover"- not "transition".
Done
p.5 Should be "two or more" not "two o more"
Done
p.6 Should be T_{ex} not Tex.
Done
