The effect of radiation pressure on the dispersal of photoevaporating discs
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Published version
Author(s)
Robinson, Alfie
Owen, James E
Booth, Richard A
Type
Journal Article
Abstract
Observed infrared (IR) excesses indicate that protoplanetary discs evolve slowly for the majority of their lifetime before losing
their near- and mid-IR excesses on short time-scales. Photoevaporation models can explain this ‘two-time-scale’ nature of disc
evolution through the removal of inner regions of discs after a few million years. However, they also predict the existence
of a population of non-accreting discs with large cavities. Such discs are scarce within the observed population, suggesting
the models are incomplete. We explore whether radiation-pressure-driven outflows are able to remove enough dust to fit
observations. We simulate these outflows using CUDISC, including dust dynamics, growth/fragmentation, radiative transfer and a
parametrization of internal photoevaporation. We find that, in most cases, dust mass-loss rates are around 5–10 times too small
to meet observational constraints. Particles are launched from the disc inner rim, however grains larger than around a micron do
not escape in the outflow, meaning mass-loss rates are too low for the initial dust masses at gap-opening. Only systems that have
smooth photoevaporation profiles with gas mass-loss rates >∼5 × 10−9M yr−1 and disc dust masses <∼1 M⊕ at the time of
gap opening can meet observational constraints; in the current models these manifest as EUV winds driven by atypically large
high-energy photon fluxes. We also find that the height of the disc’s photosphere is controlled by small grains in the outflow as
opposed to shadowing from a hot inner rim; the effect of this can be seen in synthetic scattered light observations.
their near- and mid-IR excesses on short time-scales. Photoevaporation models can explain this ‘two-time-scale’ nature of disc
evolution through the removal of inner regions of discs after a few million years. However, they also predict the existence
of a population of non-accreting discs with large cavities. Such discs are scarce within the observed population, suggesting
the models are incomplete. We explore whether radiation-pressure-driven outflows are able to remove enough dust to fit
observations. We simulate these outflows using CUDISC, including dust dynamics, growth/fragmentation, radiative transfer and a
parametrization of internal photoevaporation. We find that, in most cases, dust mass-loss rates are around 5–10 times too small
to meet observational constraints. Particles are launched from the disc inner rim, however grains larger than around a micron do
not escape in the outflow, meaning mass-loss rates are too low for the initial dust masses at gap-opening. Only systems that have
smooth photoevaporation profiles with gas mass-loss rates >∼5 × 10−9M yr−1 and disc dust masses <∼1 M⊕ at the time of
gap opening can meet observational constraints; in the current models these manifest as EUV winds driven by atypically large
high-energy photon fluxes. We also find that the height of the disc’s photosphere is controlled by small grains in the outflow as
opposed to shadowing from a hot inner rim; the effect of this can be seen in synthetic scattered light observations.
Date Issued
2025-01
Date Acceptance
2024-11-30
Citation
Monthly Notices of the Royal Astronomical Society, 2025, 536 (2), pp.1689-1709
ISSN
0035-8711
Publisher
Oxford University Press
Start Page
1689
End Page
1709
Journal / Book Title
Monthly Notices of the Royal Astronomical Society
Volume
536
Issue
2
Copyright Statement
© 2024 The Author(s).
Published by Oxford University Press on behalf of Royal Astronomical Society. This is an Open Access article distributed under the terms of the Creative
Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium,
provided the original work is properly cited.
Published by Oxford University Press on behalf of Royal Astronomical Society. This is an Open Access article distributed under the terms of the Creative
Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium,
provided the original work is properly cited.
License URL
Identifier
https://doi.org/10.1093/mnras/stae2702
Subjects
ACCRETION DISKS
Astronomy & Astrophysics
CIRCUMSTELLAR DISKS
circumstellar matter
DUST
EVOLUTION
EXTREME-ULTRAVIOLET
FAR-ULTRAVIOLET
HYDRODYNAMICS SIMULATIONS
Physical Sciences
protoplanetary discs
PROTOPLANETARY DISCS
Science & Technology
SIZE DISTRIBUTION
stars: pre-main-sequence
X-RAY PHOTOEVAPORATION
Publication Status
Published
Date Publish Online
2024-12-06