Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Mid-infrared interferometry of the massive young stellar object NGC3603
  - IRS 9A   We present observations and models for one of these MYSO candidates, NGC3603
IRS 9A. Our goal is to investigate with infrared interferometry the structure
of IRS 9A on scales as small as 200AU, exploiting the fact that a cluster of O
and B stars has blown away much of the obscuring foreground dust and gas.
Observations in the N-band were carried out with the MIDI beam combiner
attached to the VLTI. Additional interferometric observations which probe the
structure of IRS 9A on larger scales were performed with an aperture mask
installed in the T-ReCS instrument of Gemini South. The spectral energy
distribution (SED) is constrained by the MIDI N-band spectrum and by data from
the Spitzer Space Telescope. Our efforts to model the structure and SED of IRS
9A range from simple geometrical models of the brightness distribution to one-
and two-dimensional radiative transfer computations. The target is resolved by
T-ReCS, with an equivalent (elliptical) Gaussian width of 330mas by 280mas
(2300 AU by 2000 AU). Despite this fact, a warm compact unresolved component
was detected by MIDI which is possibly associated with the inner regions of a
flattened dust distribution. Based on our interferometric data, no sign of
multiplicity was found on scales between about 200AU and 700AU projected
separation. A geometric model consisting of a warm (1000 K) ring (400 AU
diameter) and a cool (140 K) large envelope provides a good fit to the data. No
single model fitting all visibility and photometric data could be found, with
disk models performing better than spherical models. While the data are clearly
inconsistent with a spherical dust distribution they are insufficient to prove
the existence of a disk but rather hint at a more complex dust distribution.

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The categories of this paper are: chem-ph
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The categories of this paper are: hep-ex
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The categories of this paper are: bayes-an
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The categories of this paper are: comp-gas
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The categories of this paper are: solv-int
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The categories of this paper are: nucl-th
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The categories of this paper are: hep-th
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The categories of this paper are: physics
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The categories of this paper are: math
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The categories of this paper are: econ
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The categories of this paper are: math-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: ao-sci
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The categories of this paper are: gr-qc
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The categories of this paper are: stat
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The categories of this paper are: cmp-lg