Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Uncertainties in water chemistry in disks: An application to TW Hya   Context. This paper discusses the sensitivity of water lines to chemical
processes and radiative transfer for the protoplanetary disk around TW Hya. The
study focuses on the Herschel spectral range in the context of new line
detections with the PACS instrument from the Gas in Protoplanetary Systems
project (GASPS). Aims. The paper presents an overview of the chemistry in the
main water reservoirs in the disk around TW Hya. It discusses the limitations
in the interpretation of observed water line fluxes. Methods. ... (abbreviated)
Results. We report new line detections of p-H2O (3_22-2_11) at 89.99 micron and
CO J=18-17 at 144.78 micron for the disk around TW Hya. Disk modeling shows
that the far-IR fine structure lines ([OI], [CII]) and molecular submm lines
are very robust to uncertainties in the chemistry, while the water line fluxes
can change by factors of a few. The water lines are optically thick,
sub-thermally excited and can couple to the background continuum radiation
field. The low-excitation water lines are also sensitive to uncertainties in
the collision rates, e.g. with neutral hydrogen. The gas temperature plays an
important role for the [OI] fine structure line fluxes, the water line fluxes
originating from the inner disk as well as the high excitation CO, CH+ and OH
lines. Conclusions. Due to their sensitivity on chemical input data and
radiative transfer, water lines have to be used cautiously for understanding
details of the disk structure. Water lines covering a wide range of excitation
energies provide access to the various gas phase water reservoirs (inside and
outside the snow line) in protoplanetary disks and thus provide important
information on where gas-phase water is potentially located. Experimental
and/or theoretical collision rates for H2O with atomic hydrogen are needed to
diminish uncertainties from water line radiative transfer.

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The categories of this paper are: patt-sol
26
The categories of this paper are: bayes-an
23
The categories of this paper are: solv-int
0
The categories of this paper are: hep-ph
27
The categories of this paper are: comp-gas
2
The categories of this paper are: math
15
The categories of this paper are: nucl-ex
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The categories of this paper are: adap-org
11
The categories of this paper are: hep-lat
35
The categories of this paper are: mtrl-th
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The categories of this paper are: chao-dyn
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The categories of this paper are: funct-an
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The categories of this paper are: atom-ph
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The categories of this paper are: q-alg
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The categories of this paper are: q-fin
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The categories of this paper are: hep-ex