Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Mapping the release of volatiles in the inner comae of comets C/2012 F6
  (Lemmon) and C/2012 S1 (ISON) using the Atacama Large
  Millimeter/Submillimeter Array   Results are presented from the first cometary observations using the Atacama
Large Millimeter/Submillimeter Array (ALMA), including measurements of the
spatially-resolved distributions of HCN, HNC, H$_2$CO and dust within the comae
of two comets: C/2012 F6 (Lemmon) and C/2012 S1 (ISON), observed at
heliocentric distances of 1.5 AU and 0.54 AU, respectively. These observations
(with angular resolution $\approx0.5''$), reveal an unprecedented level of
detail in the distributions of these fundamental cometary molecules, and
demonstrate the power of ALMA for quantitative measurements of the
distributions of molecules and dust in the inner comae of typical bright
comets. In both comets, HCN is found to originate from (or within a few hundred
km of) the nucleus, with a spatial distribution largely consistent with
spherically-symmetric, uniform outflow. By contrast, the HNC distributions are
clumpy and asymmetrical, with peaks at cometocentric radii $\sim$500-1000~km,
consistent with release of HNC in collimated outflow(s). Compared to HCN, the
H$_2$CO distribution in comet Lemmon is very extended. The interferometric
visibility amplitudes are consistent with coma production of H$_2$CO and HNC
from unidentified precursor material(s) in both comets. Adopting a Haser model,
the H$_2$CO parent scale-length is found to be a few thousand km in Lemmon and
only a few hundred km in ISON, consistent with destruction of the precursor by
photolysis or thermal degradation at a rate which scales in proportion to the
Solar radiation flux.

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The categories of this paper are: dg-ga
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The categories of this paper are: solv-int
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The categories of this paper are: stat
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The categories of this paper are: econ
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The categories of this paper are: hep-ph
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The categories of this paper are: math
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The categories of this paper are: eess
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The categories of this paper are: hep-th
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The categories of this paper are: math-ph
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The categories of this paper are: plasm-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: physics
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The categories of this paper are: mtrl-th
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The categories of this paper are: funct-an
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The categories of this paper are: hep-lat
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The categories of this paper are: hep-ex