Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Dense molecular cloud cores as a source of micrometer-sized grains in
  galaxies   Coreshine in dense molecular cloud cores (dense cores) is interpreted as
evidence for micrometer-sized grains (referred to as very large grains, VLGs).
VLGs may have a significant influence on the total dust amount and the
extinction curve. We estimate the total abundance of VLGs in the Galaxy,
assuming that dense cores are the site of VLG formation. We find that the VLG
abundance relative to the total dust mass is roughly $\phi_\mathrm{VLG}\sim
0.01(1-\epsilon )/\epsilon (\tau_\mathrm{SF}/5\times 10^9~\mathrm{yr})^{-1}
(f_\mathrm{VLG}/0.5)(t_\mathrm{shat}/10^8~\mathrm{yr})$, where $\epsilon$ is
the star formation efficiency in dense cores, $\tau_\mathrm{SF}$ the timescale
of gas consumption by star formation, $f_\mathrm{VLG}$ the fraction of dust
mass eventually coagulated into VLGs in dense cores, and $t_\mathrm{shat}$ the
lifetime of VLGs (determined by shattering). Adopting their typical values for
the Galaxy, we obtain $\phi_\mathrm{VLG}\sim 0.02$--0.09. This abundance is
well below the value detected in the heliosphere by Ulysses and Galileo, which
means that local enhancement of VLG abundance in the solar neighborhood is
required if the VLGs originate from dense cores. We also show that the effects
of VLGs on the extinction curve are negligible even with the upper value of the
above range, $\phi_\mathrm{VLG}\sim 0.09$. If we adopt an extreme value,
$\phi_\mathrm{VLG}\sim 0.5$, close to that inferred from the above spacecraft
data, the extinction curve is still in the range of the variation in Galactic
extinction curves, but is not typical of the diffuse ISM.

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The categories of this paper are: hep-ex
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The categories of this paper are: q-bio
14
The categories of this paper are: math-ph
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The categories of this paper are: patt-sol
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The categories of this paper are: ao-sci
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The categories of this paper are: dg-ga
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The categories of this paper are: gr-qc
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The categories of this paper are: nucl-ex
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The categories of this paper are: solv-int
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The categories of this paper are: mtrl-th
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The categories of this paper are: q-fin
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The categories of this paper are: hep-th
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The categories of this paper are: cond-mat
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The categories of this paper are: q-alg
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The categories of this paper are: nucl-th
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The categories of this paper are: chao-dyn