Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A Proper Motion Survey for White Dwarfs with the Wide Field Planetary
  Camera 2   We have performed a search for halo white dwarfs as high proper motion
objects in a second epoch WFPC2 image of the Groth-Westphal strip. We identify
24 high proper motion objects with mu > 0.014 ''/yr. Five of these high proper
motion objects are identified as strong white dwarf candidates on the basis of
their position in a reduced proper motion diagram. We create a model of the
Milky Way thin disk, thick disk and stellar halo and find that this sample of
white dwarfs is clearly an excess above the < 2 detections expected from these
known stellar populations. The origin of the excess signal is less clear.
Possibly, the excess cannot be explained without invoking a fourth galactic
component: a white dwarf dark halo. We present a statistical separation of our
sample into the four components and estimate the corresponding local white
dwarf densities using only the directly observable variables, V, V-I, and mu.
For all Galactic models explored, our sample separates into about 3 disk white
dwarfs and 2 halo white dwarfs. However, the further subdivision into the thin
and thick disk and the stellar and dark halo, and the subsequent calculation of
the local densities are sensitive to the input parameters of our model for each
Galactic component. Using the lowest mean mass model for the dark halo we find
a 7% white dwarf halo and six times the canonical value for the thin disk white
dwarf density (at marginal statistical significance), but possible systematic
errors due to uncertainty in the model parameters likely dominate these
statistical error bars. The white dwarf halo can be reduced to around 1.5% of
the halo dark matter by changing the initial mass function slightly. The local
thin disk white dwarf density in our solution can be made consistent with the
canonical value by assuming a larger thin disk scaleheight of 500 pc.

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The categories of this paper are: math-ph
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The categories of this paper are: cs
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The categories of this paper are: ao-sci
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The categories of this paper are: adap-org
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The categories of this paper are: hep-ex
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The categories of this paper are: hep-lat
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The categories of this paper are: q-bio
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The categories of this paper are: patt-sol
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The categories of this paper are: cmp-lg
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The categories of this paper are: hep-th
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The categories of this paper are: nucl-ex
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The categories of this paper are: math
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The categories of this paper are: cond-mat
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The categories of this paper are: gr-qc
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The categories of this paper are: hep-ph
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The categories of this paper are: alg-geom