Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A deeply embedded young protoplanetary disk around L1489 IRS observed by
  the submillimeter array   Circumstellar disks are expected to form early in the process that leads to
the formation of a young star, during the collapse of the dense molecular cloud
core. It is currently not well understood at what stage of the collapse the
disk is formed or how it subsequently evolves. We aim to identify whether an
embedded Keplerian protoplanetary disk resides in the L1489 IRS system. Given
the amount of envelope material still present, such a disk would respresent a
very young example of a protoplanetary disk. Using the Submillimeter Array
(SMA) we have observed the HCO$^+$ $J=$ 3--2 line with a resolution of about
1$''$. At this resolution a protoplanetary disk with a radius of a few hundred
AUs should be detectable, if present. Radiative transfer tools are used to
model the emission from both continuum and line data. We find that these data
are consistent with theoretical models of a collapsing envelope and Keplerian
circumstellar disk. Models reproducing both the SED and the interferometric
continuum observations reveal that the disk is inclined by 40$^\circ$ which is
significantly different to the surrounding envelope (74$^\circ$). This
misalignment of the angular momentum axes may be caused by a gradient within
the angular momentum in the parental cloud or if L1489 IRS is a binary system
rather than just a single star. In the latter case, future observations looking
for variability at sub-arcsecond scales may be able to constrain these
dynamical variations directly. However, if stars form from turbulent cores, the
accreting material will not have a constant angular momentum axis (although the
average is well defined and conserved) in which case it is more likely to have
a misalignment of the angular momentum axes of the disk and the envelope.

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The categories of this paper are: quant-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: hep-ph
37
The categories of this paper are: supr-con
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The categories of this paper are: acc-phys
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The categories of this paper are: stat
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The categories of this paper are: nucl-th
33
The categories of this paper are: plasm-ph
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The categories of this paper are: econ
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The categories of this paper are: chem-ph
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The categories of this paper are: ao-sci
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The categories of this paper are: atom-ph
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The categories of this paper are: q-bio
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The categories of this paper are: solv-int
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The categories of this paper are: q-alg
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The categories of this paper are: patt-sol