The Andromeda Galaxy and Its Star Formation History
Round 1
Reviewer 1 Report
The manuscript is not a scientific paper because it does not contain new science results, and it is not a review because it is too brief both concerning the text and the bibliography. The NASA/ADS gives 3563 papers on M31 in refereed journals since 2015 - by two orders more than is mentioned in this manuscript.
The English is OK. Some misprints are present.
Author Response
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Reviewer 1:
The manuscript is not a scientific paper because it does not contain new science results, and it is not a review because it is too brief both concerning the text and the bibliography. The NASA/ADS gives 3563 papers on M31 in refereed journals since 2015 - by two orders more than is mentioned in this manuscript.
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Author response:
It is not clear what is the reviewer asking.
Reviewer 2 Report
Dear author,
I have read the submitted manuscript "The Andromeda Galaxy and its Star Formation History” with very interest. The manuscript reviews the recent observations and studies of M31. I have some minor comments that need to be addressed by the authors before recommending publication.
Line 32-34. The sentence is not well connected to the previous sentence. In addition, not only local studies claim that dust emission is related to star formation. All studies focusing on dust emission in star-forming galaxies use the dust emission as tracer of star formation activity.
Line 45-47. The galaxy components of M31 have already illustrated in the previous paragraphs. Please report a reference for the UV observations.
Line 75-76. The sentence is not clear.
Line 102-103. The relation between disk precession, stellar winds, and accretion into the central region is no clear. Please clarify.
Line 146-147. Is it possible to explain why multi-Gaussian components are needed to reproduce the line profile?
Line 153-154. Please quantify the overestimation of dust temperature and dust mass.
Line 231. It is not explained what streams C and D are
Author Response
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Reviewer 2:
Dear author,
I have read the submitted manuscript "The Andromeda Galaxy and its Star Formation History” with very interest. The manuscript reviews the recent observations and studies of M31. I have some minor comments that need to be addressed by the authors before recommending publication.
Line 32-34. The sentence is not well connected to the previous sentence. In addition, not only local studies claim that dust emission is related to star formation. All studies focusing on dust emission in star-forming galaxies use the dust emission as tracer of star formation activity.
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Author response:
The sentence has been reworded to make it more clear.
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Line 45-47. The galaxy components of M31 have already illustrated in the previous paragraphs. Please report a reference for the UV observations.
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Author response: References have been added for the instrument and the satellite.
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Line 75-76. The sentence is not clear.
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Author response:
The sentence has been corrected, with reference to NED (Nasa's Extragalactic Database)
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Line 102-103. The relation between disk precession, stellar winds, and accretion into the central region is no clear. Please clarify.
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Author response:
Another sentence has been added and a literature reference.
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Line 146-147. Is it possible to explain why multi-Gaussian components are needed to reproduce the line profile?
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Author response:
extra text has been added: the multi-Gaussian lineshape is observed and it results in large uncertainties in optically thick HI.
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Line 153-154. Please quantify the overestimation of dust temperature and dust mass.
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Author response:
The reference included the size effect on temperature but did not include the size of the effect on dust mass.
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Line 231. It is not explained what streams C and D are
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Author response:
A sentence has been added indicating their location and with reference to Fig. 3 of Conn et al. 2016
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Reviewer 3 Report
All required comments and suggestions are described in the attached pdf.
Comments for author File: 
Comments.pdf
Minor correction will improve the presentation.
Author Response
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Reviewer 3 (copied from the pdf from the reviewer):
The author gives a brief review of current study of the star formation (SF) history of the galaxy M31 (Andromeda).
The addressed topic is very interesting and timely, particularly accounting the fact that during the last couple of years an extensive study of star formation is becoming possible practically in the entire post-recombination universe.
In this sense, particular structural and spectral features observed in galaxies of local universe can be matched to the ones of cosmic dawn.
The author with his expertise can provide a first-hand information.
Therefore, I recomend publication of the presented manuscipt in Universe journal. However, before publication I would suggest to reword a few sentences being stylistically weak or not quite clear in the essence.
The comments are as follows:
1. lines 28-32: "formation history" is repeated 4 times.
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Author response:
The two sentences (lines 28-32) have been rewritten.
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2. line 53 (optional): "I.e" in the beginning of sentense sounds slightly awkward.
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Author response:
The "i.e." is unnecessary and has been removed.
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3. line 82-85: "... most of the luminosity is converted to far infrared radiation by the dust." Does this conclusion mean that most of UV radiation is absorbed by dust? If so one has to expect that optical depth is tau_uv > 1, and effects of reddening for stellar population are to be considerable? Is this really observed in M31?
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Author response: The visual (internal) extinction for M31 is ~1 mag (range 0.2-2), yielding UV extinction of ~2.5 mag (range 0.5-5). 2.5 magnitudes is a factor of 10 (optical depth of 2.3). Thus the reddenning is important for UV. The wording has been changed.
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4. line 95-99: "...which is formed by violent relaxation early in the formation of the galaxy..." Violent relaxation suggests that the bulge populations are to be close to the equilibrium (relaxed) state. The existence of 8 components seems to show that
instead the system does not yet equilibrated. Commets would help to understand this
apparent contradiction.
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Author response:
That paragraph has been expanded by adding comments at the middle and at the end.
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5. line 105-107 (optional): in this form the sentense sounds stilistically not quite consistent: by "several populations" the author means groups of stellar sources (planetary nebulae, X-ray sources etc) and stellar populations as such (thin, thick disks, bulge, and stellar clusters). It would make sense to reword this introductory sentense, and perhaps, even devide the section by a few relevant subsectons.
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Author response:
"source populations" has been replaced by "types of sources" to avoid confusion.
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6. line 156-157: "The dust clumps are mostly located in a plane..." It is worth to mention of how the location of dust clumps in plane was identified in a face-on galaxy.
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Author response:
A statement is added describing how Dong et al 2016 inferred the dust distribution.
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7. line 199: panel (a)- what is indicated by blue circles?
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Author response:
The age range indicated by the blue circles has been added to the figure caption.
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8. line 202: panel (b) at R > 0:2 degrees two distinct populations are seen. Comments
would be at least interesting.
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Author response: a remark has been added (at the end of section 5) on the association of the clusters with the spiral arms.
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9. line 206-213: it makes sense to link the description from line 206 to 212 with the right panel of Fig 3. For instance, for presented discussion it does not look quite obvious how the two populations at R > 0:2 and with ages~ 30 and ~ 100 Myr are linked to those discussed here.
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Author response:
The paragraph has been reworded, emphasizing that ref [35] was a total light study and [36] is a cluster study, which is more sensitive to young stars.
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10. line 220 (optional): rewording or more explicit description "early formation of density fluctuation".
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Author response:
The first sentence of section 6 has been rewritten to be more clear.
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11. lines 254-256: is the conclusion "This is consistent... ... its history." because more massive satelites are supposed to be more metal enriched? The underlying arguments (references) are worth.
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Author response: Yes, the giant stellar stream and smooth inner halo are more metal rich. References have been added.
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My overall opinion about the manuscript is positive and therefore I recommend it for
publication in the journal \Universe" after minor changes.
