Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Chemistry and kinematics of the pre-stellar core L1544: Constraints from
  H2D+   This paper explores the sensitivity of line profiles of H2D+, HCO+ and N2H+,
observed towards the center of L1544, to various kinematic and chemical
parameters. The total width of the H2D+ line can be matched by a static model
and by models invoking ambipolar diffusion and gravitational collapse. The
derived turbulent line width is b=0.15 km/s for the static case and <~ 0.05
km/s for the collapse case. However, line profiles of HC18O+ and N2H+ rule out
the static solution. The double-peaked H2D+ line shape requires either infall
speeds in the center that are much higher than predicted by ambipolar diffusion
models, or a shell-type distribution of H2D+, as is the case for HCO+ and N2H+.
At an offset of ~20 arcsec from the dust peak, the H2D+ abundance drops by a
factor of ~5.

2
The categories of this paper are: math
16
The categories of this paper are: stat
10
The categories of this paper are: q-bio
28
The categories of this paper are: alg-geom
1
The categories of this paper are: cs
37
The categories of this paper are: supr-con
9
The categories of this paper are: nlin
33
The categories of this paper are: plasm-ph
5
The categories of this paper are: gr-qc
27
The categories of this paper are: comp-gas
21
The categories of this paper are: adap-org
14
The categories of this paper are: math-ph
25
The categories of this paper are: patt-sol
34
The categories of this paper are: chem-ph
17
The categories of this paper are: q-fin
32
The categories of this paper are: atom-ph