Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: First phase space portrait of a hierarchical stellar structure in the
  Milky Way   We present the first detailed observational picture of a possible ongoing
massive cluster hierarchical assembly in the Galactic disk as revealed by the
analysis of the stellar full phase-space (3D positions and kinematics and
spectro-photometric properties) of an extended area ($6^{\circ}$ diameter)
surrounding the well-known $\it h$ and $\chi$ Persei double stellar cluster in
the Perseus Arm. Gaia-EDR3 shows that the area is populated by seven co-moving
clusters, three of which were previously unknown, and by an extended and quite
massive ($M\sim10^5 M_{\odot}$) halo. All stars and clusters define a complex
structure with evidence of possible mutual interactions in the form of
intra-cluster over-densities and/or bridges. They share the same chemical
abundances (half-solar metallicity) and age ($t\sim20$ Myr) within a small
confidence interval and the stellar density distribution of the surrounding
diffuse stellar halo resembles that of a cluster-like stellar system. The
combination of these evidences suggests that stars distributed within a few
degrees from $\it h$ and $\chi$ Persei are part of a common, sub-structured
stellar complex that we named LISCA I. Comparison with results obtained through
direct $N$-body simulations suggest that LISCA I may be at an intermediate
stage of an ongoing cluster assembly that can eventually evolve in a relatively
massive (a few $10^5 M_{\odot}$) stellar system. We argue that such cluster
formation mechanism may be quite efficient in the Milky Way and disk-like
galaxies and, as a consequence, it has a relevant impact on our understanding
of cluster formation efficiency as a function of the environment and redshift.

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The categories of this paper are: alg-geom
30
The categories of this paper are: q-alg
34
The categories of this paper are: chem-ph
10
The categories of this paper are: q-bio
15
The categories of this paper are: nucl-ex
36
The categories of this paper are: cmp-lg
8
The categories of this paper are: hep-ex
25
The categories of this paper are: patt-sol
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The categories of this paper are: comp-gas
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The categories of this paper are: solv-int
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The categories of this paper are: funct-an
11
The categories of this paper are: hep-lat
9
The categories of this paper are: nlin
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The categories of this paper are: dg-ga
32
The categories of this paper are: atom-ph
20
The categories of this paper are: acc-phys