Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Extra-planar H I in the Inner Milky Way   The extra-planar H I in the inner parts of the Milky Way has been discovered
to contain numerous cloud-like structures when observed in the 21cm line with
the Green Bank Telescope (GBT). These halo clouds have motions consistent with
Galactic rotation and do not seem to be related to the classic high-velocity
clouds. They are found to distances >1 kpc from the plane and can contain
hundreds of solar masses of H I. Spectra of many of the halo clouds show
evidence of coexisting cool and warm H I phases. A preliminary high-resolution
study of one of the clouds suggests that it consists of a diffuse envelope and
a few dense cores, with a peak H I column density reaching 4 x 10^20 cm^-2. The
clouds are often organized into larger structures, one example of which was
discovered near 35 degrees Galactic longitude rising higher than 2 kpc above
the Galactic plane. New observations should answer some fundamental questions
about the nature of these clouds.

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The categories of this paper are: mtrl-th
4
The categories of this paper are: cond-mat
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The categories of this paper are: q-fin
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The categories of this paper are: cmp-lg
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The categories of this paper are: nucl-ex
9
The categories of this paper are: nlin
0
The categories of this paper are: hep-ph
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The categories of this paper are: ao-sci
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The categories of this paper are: eess
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The categories of this paper are: funct-an
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The categories of this paper are: atom-ph
18
The categories of this paper are: econ
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The categories of this paper are: comp-gas
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The categories of this paper are: adap-org
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The categories of this paper are: quant-ph
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The categories of this paper are: acc-phys