Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Structure and Evolution of Young Stellar Clusters   We examine the properties of embedded clusters within 1 kiloparsec using new
data from the Spitzer Space Telescope, as well as recent results from 2MASS and
other ground-based near-infrared surveys. We use surveys of entire molecular
clouds to understand the range and distribution of cluster membership, size and
surface density. The Spitzer data demonstrate clearly that there is a continuum
of star- forming environments, from relative isolation to dense clusters. The
number of members of a cluster is correlated with the cluster radius, such that
the average surface density of clusters having a few to a thousand members
varies by a factor of only a few. The spatial distributions of
Spitzer-identified young stellar objects frequently show elongation, low
density halos, and sub-clustering. The spatial distributions of protostars
resemble the distribution of dense molecular gas, suggesting that their
morphologies result directly from the fragmentation of the natal gas. We also
examine the effects of the cluster environments on star and planet formation.
Although Far-UV and Extreme-UV radiation from massive stars can truncate disks
in a few million years, fewer than half of the young stars in our sample
(embedded clusters within 1 kpc) are found in regions of strong FUV and EUV
fields. Typical volume densities and lifetimes of the observed clusters suggest
that dynamical interactions are not an important mechanism for truncating disks
on solar system size scales.

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The categories of this paper are: cmp-lg
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The categories of this paper are: stat
18
The categories of this paper are: econ
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The categories of this paper are: eess
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The categories of this paper are: adap-org
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The categories of this paper are: nucl-th
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The categories of this paper are: q-fin
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The categories of this paper are: math
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The categories of this paper are: plasm-ph
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The categories of this paper are: physics
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The categories of this paper are: atom-ph
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The categories of this paper are: solv-int
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The categories of this paper are: alg-geom
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The categories of this paper are: funct-an
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The categories of this paper are: math-ph
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The categories of this paper are: comp-gas