Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Emission Lines from the Gas Disk around TW Hydra and the Origin of the
  Inner Hole   We compare line emission calculated from theoretical disk models with optical
to sub-millimeter wavelength observational data of the gas disk surrounding TW
Hya and infer the spatial distribution of mass in the gas disk. The model disk
that best matches observations has a gas mass ranging from
$\sim10^{-4}-10^{-5}$\ms\ for $0.06{\rm AU} <r<3.5$AU and $\sim 0.06$\ms\ for $
3.5 {\rm AU} <r<200$AU. We find that the inner dust hole ($r<3.5$AU) in the
disk must be depleted of gas by $\sim 1-2$ orders of magnitude compared to the
extrapolated surface density distribution of the outer disk. Grain growth alone
is therefore not a viable explanation for the dust hole. CO vibrational
emission arises within $r\sim 0.5$AU from thermal excitation of gas. [OI]
6300\AA\ and 5577\AA\ forbidden lines and OH mid-infrared emission are mainly
due to prompt emission following UV photodissociation of OH and water at
$r\lesssim0.1$AU and at $r\sim 4$AU. [NeII] emission is consistent with an
origin in X-ray heated neutral gas at $r\lesssim 10$AU, and may not require the
presence of a significant EUV ($h\nu>13.6$eV) flux from TW Hya. H$_2$ pure
rotational line emission comes primarily from $r\sim 1-30$AU. [OI]63$\mu$m,
HCO$^+$ and CO pure rotational lines all arise from the outer disk at
$r\sim30-120$AU. We discuss planet formation and photoevaporation as causes for
the decrease in surface density of gas and dust inside 4 AU. If a planet is
present, our results suggest a planet mass $\sim 4-7$M$_J$ situated at $\sim
3$AU. Using our photoevaporation models and the best surface density profile
match to observations, we estimate a current photoevaporative mass loss rate of
$4\times10^{-9}$\ms\ yr$^{-1}$ and a remaining disk lifetime of $\sim 5$
million years.

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The categories of this paper are: ao-sci
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The categories of this paper are: hep-ph
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The categories of this paper are: econ
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The categories of this paper are: eess
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The categories of this paper are: stat
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The categories of this paper are: patt-sol
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The categories of this paper are: acc-phys
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The categories of this paper are: nucl-th
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The categories of this paper are: alg-geom
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The categories of this paper are: supr-con
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The categories of this paper are: nlin
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The categories of this paper are: hep-lat
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The categories of this paper are: atom-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: cmp-lg
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The categories of this paper are: physics