Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Structure of Halo Gas Around M33   Understanding the distribution of gas in and around galaxies is vital for our
interpretation of galaxy formation and evolution. As part of the Arecibo Galaxy
Environment Survey (AGES) we have observed the neutral hydrogen (HI) gas in and
around the nearby Local Group galaxy M33 to a greater depth than previous
observations. As part of this project we investigated the absence of optically
detected dwarf galaxies in its neighbourhood, which is contrary to predictions
of galaxy formation models. We observed 22 discrete clouds, 11 of which were
previously undetected and none of which have optically detected counterparts.
We find one particularly interesting hydrogen cloud, which has many similar
characteristics to hydrogen distributed in the disk of a galaxy. This cloud, if
it is at the distance of M33, has a HI mass of around 10^7 Msun and a diameter
of 18 kpc, making it larger in size than M33 itself.

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The categories of this paper are: math-ph
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The categories of this paper are: q-fin
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The categories of this paper are: chem-ph
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The categories of this paper are: quant-ph
37
The categories of this paper are: supr-con
3
The categories of this paper are: physics
35
The categories of this paper are: mtrl-th
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The categories of this paper are: adap-org
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The categories of this paper are: comp-gas
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The categories of this paper are: eess
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The categories of this paper are: hep-ph
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The categories of this paper are: solv-int
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The categories of this paper are: math
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The categories of this paper are: econ
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The categories of this paper are: cmp-lg
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The categories of this paper are: nucl-ex