Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Molecular ions in L1544. I. Kinematics   We have mapped the dense dark core L1544 in H13CO+(1-0), DCO+(2-1),
DCO+(3-2), N2H+(1-0), NTH+(3-2), N2D+(2-1), N2D+(3-2), C18O(1-0), and C17O(1-0)
using the IRAM 30-m telescope. We have obtained supplementary observations of
HC18O+(1-0), HC17O+(1-0), and D13CO+(2-1). Many of the observed maps show a
general correlation with the distribution of dust continuum emission in
contrast to C18O(1-0) and C17O(1-0) which give clear evidence for depletion of
CO at positions close to the continuum peak. In particular N2D+(2-1) and (3-2)
and to a lesser extent N2H+(1-0) appear to be excellent tracers of the dust
continuum. We find that the tracers of high density gas (in particular N2D+)
show a velocity gradient along the minor axis of the L1544 core and that there
is evidence for larger linewidths close to the dust emission peak. We interpret
this using the model of the L1544 proposed by Ciolek & Basu (2000) and by
comparing the observed velocities with those expected on the basis of their
model. The results show reasonable agreement between observations and model in
that the velocity gradient along the minor axis and the line broadening toward
the center of L1544 are predicted by the model. This is evidence in favour of
the idea that amipolar diffusion across field lines is one of the basic
processes leading to gravitational collapse. However, line widths are
significantly narrower than observed and are better reproduced by the Myers &
Zweibel (2001) model which considers the quasistatic vertical contraction of a
layer due to dissipation of its Alfvenic turbulence, indicating the importance
of this process for cores in the verge of forming a star.

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The categories of this paper are: bayes-an
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The categories of this paper are: hep-ph
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The categories of this paper are: cond-mat
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The categories of this paper are: adap-org
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The categories of this paper are: q-fin
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The categories of this paper are: physics
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The categories of this paper are: cmp-lg
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The categories of this paper are: econ
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The categories of this paper are: patt-sol
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The categories of this paper are: solv-int
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The categories of this paper are: supr-con
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The categories of this paper are: nlin
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The categories of this paper are: nucl-th
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The categories of this paper are: chao-dyn
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The categories of this paper are: nucl-ex
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The categories of this paper are: dg-ga