Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Ultraviolet Extinction Properties in the Milky Way   We have assembled a homogeneous database of 417 ultraviolet (UV) extinction
curves for reddened sightlines having International Ultraviolet Explorer (IUE)
spectra. We have combined these with optical and 2MASS photometry allowing
estimates of the ratio of total-to-selective extinction, R(V), for the entire
sample. Fitzpatrick-Massa (FM) parameters have also been found for the entire
sample. This is the largest study of parameterized UV extinction curves yet
published and it covers a wide range of environments, from dense molecular
clouds to the diffuse interstellar medium (ISM), with extinctions A(V) ranging
from 0.50 to 4.80. It is the first to extend far beyond the solar neighborhood
and into the Galaxy at large, with 30 sightlines having distances > 5 kpc.
Previously, the longest sightlines with FM parameters and R(V) extended ~ 1
kpc. We find that (1.) the CCM extinction law applies for 93% of the
sightlines, implying that dust processing in the Galaxy is efficient and
systematic; (2.) the central wavelength of the 2175 A bump is constant; (3.)
the 2175 A bump width is dependent on environment. Only four sightlines show
systematic deviations from CCM, HD 29647, 62542, 204827, and 210121. These
sightlines all sample dense, molecule-rich clouds. The new extinction curves
and values of R(V) allow us to revise the CCM law.

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The categories of this paper are: patt-sol
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The categories of this paper are: nlin
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The categories of this paper are: atom-ph
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The categories of this paper are: plasm-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: q-fin
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The categories of this paper are: stat
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The categories of this paper are: alg-geom
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The categories of this paper are: cs
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The categories of this paper are: gr-qc
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The categories of this paper are: hep-th
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The categories of this paper are: comp-gas
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The categories of this paper are: hep-lat
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The categories of this paper are: hep-ex
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The categories of this paper are: nucl-ex
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The categories of this paper are: math-ph