Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Searching for Stars in Compact High-Velocity Clouds. I First Results
  from VLT and 2MASS   We investigate the hypothesis that compact high-velocity clouds (CHVC) are
the "missing" dwarf galaxies of the Local Group, by searching them for
populations of resolved stars. To this end we conducted two distinct tests
based on optical and near-infrared single-star photometry. The optical and the
near-infrared experiments complement one another; the optical data help us to
rule out distant populations but they are restricted to the central regions of
the gas distributions, whereas the near-infrared photometry allows us to set
limits on nearby populations spread over the typical cloud size. First, we
discuss deep optical single-star photometry of five CHVCs in the V and I
filters, obtained with the FORS instrument at the Very Large Telecope (VLT). We
find that their optical colour-magnitude diagrams are indistinguishable from
that of a population of Galactic stars, and attribute all of the resolved stars
to Galactic foreground. We present simulations which address the question of
how much of a "normal" dwarf-galaxy type population we might hide in the data.
A Kolmogorov-Smirnov test allows us to set very stringent limits on the absence
of a resolved stellar population in CHVCs. Second, we also culled near infrared
single-star photometry in the J, H, and K_S bands for four of the CHVCs from
the Two Micron All Sky Survey (2MASS). The infrared data do not reveal any
stellar contents in the CHVCs which resembles that of nearby dwarf galaxies
either, and are explained with Galactic foreground as well. We interpret our
null detections to indicate that the five CHVCs investigated by us do not host
an associated stellar content which is similar to that of the known dwarf
galaxies of the Local Group. These CHVCs are very likely pure hydrogen clouds
in which no star formation has taken place over cosmic time.

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The categories of this paper are: adap-org
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The categories of this paper are: alg-geom
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The categories of this paper are: cond-mat
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The categories of this paper are: supr-con
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The categories of this paper are: nucl-ex
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The categories of this paper are: econ
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The categories of this paper are: ao-sci
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The categories of this paper are: atom-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: mtrl-th
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The categories of this paper are: cmp-lg
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The categories of this paper are: eess
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The categories of this paper are: dg-ga
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The categories of this paper are: hep-th
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The categories of this paper are: stat
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The categories of this paper are: cs