Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Molecules with ALMA at Planet-forming Scales (MAPS). XV. Tracing
  protoplanetary disk structure within 20 au   Constraining the distribution of gas and dust in the inner 20 au of
protoplanetary disks is difficult. At the same time, this region is thought to
be responsible for most planet formation, especially around the water ice line
at 3-10 au. Under the assumption that the gas is in a Keplerian disk, we use
the exquisite sensitivity of the Molecules with ALMA at Planet-forming Scales
(MAPS) ALMA large program to construct radial surface brightness profiles with
a ~3 au effective resolution for the CO isotopologue J=2-1 lines using the line
velocity profile. IM Lup reveals a central depression in 13CO and C18O that is
ascribed to a pileup of ~500 $M_\oplus$ of dust in the inner 20 au, leading to
a gas-to-dust ratio of around <10. This pileup is consistent with efficient
drift of grains ($\gtrsim$ 100 $M_\oplus$ Myr$^{-1}$) and a local gas-to-dust
ratio that suggests that the streaming instability could be active. The CO
isotopologue emission in the GM Aur disk is consistent with a small (~15 au),
strongly depleted gas cavity within the ~40 au dust cavity. The radial surface
brightness profiles for both the AS 209 and HD 163296 disks show a local
minimum and maximum in the C18O emission at the location of a known dust ring
(~14 au) and gap (~10 au), respectively. This indicates that the dust ring has
a low gas-to-dust ratio ($>$ 10) and that the dust gap is gas-rich enough to
have optically thick C18O.

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The categories of this paper are: nucl-th
27
The categories of this paper are: comp-gas
31
The categories of this paper are: ao-sci
16
The categories of this paper are: stat
18
The categories of this paper are: econ
5
The categories of this paper are: gr-qc
19
The categories of this paper are: eess
22
The categories of this paper are: chao-dyn
36
The categories of this paper are: cmp-lg
9
The categories of this paper are: nlin
8
The categories of this paper are: hep-ex
35
The categories of this paper are: mtrl-th
0
The categories of this paper are: hep-ph
30
The categories of this paper are: q-alg
32
The categories of this paper are: atom-ph
26
The categories of this paper are: bayes-an