Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: ALMA observations of the Extended Green Object G19.01$-$0.03: I. A
  Keplerian disc in a massive protostellar system   Using the Atacama Large Millimetre/submillimeter Array (ALMA) and the Karl G.
Jansky Very Large Array (VLA), we observed the Extended Green Object (EGO)
G19.01$-$0.03 with sub-arcsecond resolution from 1.05 mm to 5.01 cm
wavelengths. Our $\sim0.4''\sim1600$ AU angular resolution ALMA observations
reveal a velocity gradient across the millimetre core MM1, oriented
perpendicular to the previously known bipolar molecular outflow, that is
consistently traced by 20 lines of 8 molecular species with a range of
excitation temperatures, including complex organic molecules (COMs). Kinematic
modelling shows the data are well described by models that include a disc in
Keplerian rotation and infall, with an enclosed mass of $40-70
\mathrm{M}_{\odot}$ (within a 2000 AU outer radius) for a disc inclination
angle of $i=40^{\circ}$, of which $5.4-7.2 \mathrm{M}_{\odot}$ is attributed to
the disc. Our new VLA observations show that the 6.7 GHz Class II methanol
masers associated with MM1 form a partial ellipse, consistent with an inclined
ring, with a velocity gradient consistent with that of the thermal gas. The
disc-to-star mass ratio suggests the disc is likely to be unstable and may be
fragmenting into as-yet-undetected low mass stellar companions. Modelling the
centimetre--millimetre spectral energy distribution of MM1 shows the ALMA 1.05
mm continuum emission is dominated by dust, whilst a free-free component,
interpreted as a hypercompact HII region, is required to explain the VLA
$\sim$5 cm emission. The high enclosed mass derived for a source with a
moderate bolometric luminosity ($\sim$10$^{4} \mathrm{L}_{\odot}$) suggests
that the MM1 disc may feed an unresolved high-mass binary system.

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The categories of this paper are: q-fin
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The categories of this paper are: adap-org
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The categories of this paper are: atom-ph
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The categories of this paper are: eess
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The categories of this paper are: nlin
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The categories of this paper are: comp-gas
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The categories of this paper are: gr-qc
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The categories of this paper are: supr-con
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The categories of this paper are: alg-geom
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The categories of this paper are: cs
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The categories of this paper are: mtrl-th
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The categories of this paper are: math-ph
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The categories of this paper are: q-alg
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The categories of this paper are: acc-phys
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The categories of this paper are: bayes-an
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The categories of this paper are: solv-int