Dust clearing by radial drift in evolving protoplanetary disks. (arXiv:2004.02918v1 [astro-ph.EP])

Dust clearing by radial drift in evolving protoplanetary disks. (arXiv:2004.02918v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Appelgren_J/0/1/0/all/0/1">Johan Appelgren</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lambrechts_M/0/1/0/all/0/1">Michiel Lambrechts</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Johansen_A/0/1/0/all/0/1">Anders Johansen</a>

Recent surveys have revealed that protoplanetary disks typically have dust
masses that appear to be insufficient to account for the high occurrence rate
of exoplanet systems. We demonstrate that this observed dust depletion is
consistent with the radial drift of pebbles. Using a Monte Carlo method we
simulate the evolution of a cluster of protoplanetary disks, using a 1D
numerical method to viscously evolve each gas disk together with the radial
drift of dust particles that have grown to 100 $mu$m in size. For a 2 Myr old
cluster of stars, we find a slightly sub-linear scaling between the gas disk
mass and the gas accretion rate ($M_mathrm{g}proptodot{M}^{0.9}$). However,
for the dust mass we find that evolved dust disks have a much weaker scaling
with the gas accretion rate, with the precise scaling depending on the age at
which the cluster is sampled and the intrinsic age spread of the disks in the
cluster. Ultimately, we find that the dust mass present in protoplanetary disk
is on the order of 10-100 Earth masses in 1-3 Myr old star-forming regions, a
factor of 10 to 100 depleted from the original dust budget. As the dust drains
from the outer disk, pebbles pile up in the inner disk and locally increase the
dust-to-gas ratio by a factor of up to 4 above the initial value. In these high
dust-to-gas ratio regions we find conditions that are favourable for
planetesimal formation via the streaming instability and subsequent growth by
pebble accretion. We also find the following scaling relations with stellar
mass within a 1-2 Myr old cluster: a slightly super-linear scaling between the
gas accretion rate and stellar mass ($dot{M}propto M_star^{1.4}$), a
slightly super-linear scaling between the gas disk mass and the stellar mass
($M_mathrm{g}propto M_star^{1.4}$) and a super-linear relation between the
dust disk mass and stellar mass ($M_mathrm{d}propto M_star^{1.4-4.1}$).

Recent surveys have revealed that protoplanetary disks typically have dust
masses that appear to be insufficient to account for the high occurrence rate
of exoplanet systems. We demonstrate that this observed dust depletion is
consistent with the radial drift of pebbles. Using a Monte Carlo method we
simulate the evolution of a cluster of protoplanetary disks, using a 1D
numerical method to viscously evolve each gas disk together with the radial
drift of dust particles that have grown to 100 $mu$m in size. For a 2 Myr old
cluster of stars, we find a slightly sub-linear scaling between the gas disk
mass and the gas accretion rate ($M_mathrm{g}proptodot{M}^{0.9}$). However,
for the dust mass we find that evolved dust disks have a much weaker scaling
with the gas accretion rate, with the precise scaling depending on the age at
which the cluster is sampled and the intrinsic age spread of the disks in the
cluster. Ultimately, we find that the dust mass present in protoplanetary disk
is on the order of 10-100 Earth masses in 1-3 Myr old star-forming regions, a
factor of 10 to 100 depleted from the original dust budget. As the dust drains
from the outer disk, pebbles pile up in the inner disk and locally increase the
dust-to-gas ratio by a factor of up to 4 above the initial value. In these high
dust-to-gas ratio regions we find conditions that are favourable for
planetesimal formation via the streaming instability and subsequent growth by
pebble accretion. We also find the following scaling relations with stellar
mass within a 1-2 Myr old cluster: a slightly super-linear scaling between the
gas accretion rate and stellar mass ($dot{M}propto M_star^{1.4}$), a
slightly super-linear scaling between the gas disk mass and the stellar mass
($M_mathrm{g}propto M_star^{1.4}$) and a super-linear relation between the
dust disk mass and stellar mass ($M_mathrm{d}propto M_star^{1.4-4.1}$).

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