A Scattered Star Group in the Orion A Region of the Milky Way
, Kristina Lyzenko 1,2, Anatoly Kalinkin 1,3, Nikolay Kondratev 1,2, Dana Kovaleva 1,†and Sergei Sapozhnikov 1Round 1
Reviewer 1 Report
.
Comments for author File: 
Comments.pdf
Already detailed above.
Author Response
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Author Response File: Author Response.pdf
Reviewer 2 Report
The paper "Scattered star group in the Milky Way — kinematics in Orion A" by S. Vereshchagin et al. deals with the identification of a scattered group in the vicinity of the Orion A gas cloud.
The paper is very clearly written and the approach followed in the data analysis is state-of-the-art. The authors made a selection of two samples of probable candidates for the Group. In the following, I list a few minor issues and one major concern (**) that should be addressed before I feel confident to recommend this paper for acceptance.
* The title does not read well. Maybe a straight "A scattered star group in the Orion A region of the Milky Way" sounds better.
* Fig. 3 gives an idea of the spatial distribution of the stars of the group, and should shown at the beginning. Combining Fig.1,2,3 would do.
* Section 2.3: please give some basic information on the clustering algorithm; for example, supervised or unsupervised?
* Contamination is addressed properly. However, there is no satisfactory mention of the efficiency of the method to isolate group members i.e., how many may have been lost.
** p. 11, Discussion: I am surprised by how the authors develop their conclusion. Much more emphasis should be given to the radial velocity dispersion, as the PMD provides a biased view of the group member motions, also in light of the much larger radial velocity of the group (Vt ~ 3.6 km/s, Vr ~ 26.5 km/s).
l. 215: "The relative error of the mean radial velocity for Dataset B eRV ~ 8%, i.e. two times larger. Thus, we use the approach based purely on the tangential velocities." This does not seem a strong enough justification.
l. 229 The authors acknowledge that the validity of the orbit reconstruction based on proper motion is limited, but then the backward integration with radial velocity included should be presented first.
l. 230-231: it is not clear whether they have attempted to make an orbit reconstruction after correction for uncertainties in radial velocity, and how this might affect their conclusion. This should be attempted.
* l. 254 verb is missing in the sentence
No problem with English language.
Author Response
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Author Response File: Author Response.pdf
