Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Are Newly Discovered HI High Velocity Clouds Minihalos in the Local
  Group?   A set of HI sources extracted from the north Galactic polar region by the
ongoing ALFALFA survey has properties that are consistent with the
interpretation that they are associated with isolated minihalos in the
outskirts of the Local Group (LG). Unlike objects detected by previous surveys,
such as the Compact High Velocity Clouds of Braun & Burton (1999), the HI
clouds found by ALFALFA do not violate any structural requirements or halo
scaling laws of the LambdaCDM structure paradigm, nor would they have been
detected by extant HI surveys of nearby galaxy groups other than the LG. At a
distance of d Mpc, their HI masses range between $5 x 10^4 d^2 and 10^6 d^2
solar and their HI radii between <0.4d and 1.6 d kpc. If they are parts of
gravitationally bound halos, the total masses would be on order of 10^8--10^9
solar, their baryonic content would be signifcantly smaller than the cosmic
fraction of 0.16 and present in a ionized gas phase of mass well exceeding that
of the neutral phase. This study does not however prove that the minihalo
interpretation is unique. Among possible alternatives would be that the clouds
are shreds of the Leading Arm of the Magellanic Stream.

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The categories of this paper are: patt-sol
15
The categories of this paper are: nucl-ex
12
The categories of this paper are: nucl-th
13
The categories of this paper are: quant-ph
5
The categories of this paper are: gr-qc
4
The categories of this paper are: cond-mat
31
The categories of this paper are: ao-sci
22
The categories of this paper are: chao-dyn
32
The categories of this paper are: atom-ph
10
The categories of this paper are: q-bio
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The categories of this paper are: plasm-ph
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The categories of this paper are: eess
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The categories of this paper are: supr-con
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The categories of this paper are: dg-ga
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The categories of this paper are: comp-gas
1
The categories of this paper are: cs