Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Four highly luminous massive star forming regions in the Norma Spiral
  Arm.: I. Molecular gas and dust observations   We report molecular line and dust continuum observations, made with the SEST
telescope, towards four young high-mass star forming regions associated with
highly luminous (L> 6x10^5 Lsun) IRAS sources (15290-5546, 15502-5302,
15567-5236 and 16060-5146). Molecular emission was mapped in lines of CS
(J=2-1, 3-2 and 5-4), SiO (J=2-1 and 3-2), CH3OH (Jk=3k-2k and 2k-1k), and C34S
(J=3-2). In addition, single spectra at the peak position were taken in the CO,
13CO and C18O (J=1-0) lines. We find that the luminous star forming regions are
associated with molecular gas and dust structures with radii of typically 0.5
pc, masses of ~5x10^3 Msun, column densities of ~5x10^{23} cm^{-2}, molecular
hydrogen densities of typically ~2x10^5 cm^{-3} and dust temperatures of ~40 K.
The 1.2 mm dust continuum observations further indicate that the cores are
centrally condensed, having radial density profiles with power-law indices in
the range 1.6-1.9. We find that under these conditions dynamical friction by
the gas plays an important role in the migration of high-mass stars towards the
central core region, providing an explanation for the observed stellar mass
segregation within the cores.

18
The categories of this paper are: econ
17
The categories of this paper are: q-fin
9
The categories of this paper are: nlin
4
The categories of this paper are: cond-mat
29
The categories of this paper are: funct-an
19
The categories of this paper are: eess
37
The categories of this paper are: supr-con
10
The categories of this paper are: q-bio
22
The categories of this paper are: chao-dyn
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The categories of this paper are: bayes-an
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The categories of this paper are: acc-phys
1
The categories of this paper are: cs
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The categories of this paper are: atom-ph
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The categories of this paper are: comp-gas
2
The categories of this paper are: math
8
The categories of this paper are: hep-ex