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The formation and fate of planetesimals at planetary gap edges

Eriksson, Linn LU (2022)
Abstract
High resolution observations with ALMA have revealed that concentric rings and gaps are common features in protoplanetary disks. The favored mechanism for creating these substructures are planet-disk interactions, in which growing planets open gaps in the disk, and particles become trapped at the pressure maxima that form at the corresponding gap edges. Since the particle density in these pressure bumps can become much higher than the global value, they are likely sites for planetesimal formation via the streaming instability.

In a series of three papers, we have studied the formation and fate of such planetesimals formed at planetary gap edges. By performing global simulations of an evolving disk perturbed by multiple planets,... (More)
High resolution observations with ALMA have revealed that concentric rings and gaps are common features in protoplanetary disks. The favored mechanism for creating these substructures are planet-disk interactions, in which growing planets open gaps in the disk, and particles become trapped at the pressure maxima that form at the corresponding gap edges. Since the particle density in these pressure bumps can become much higher than the global value, they are likely sites for planetesimal formation via the streaming instability.

In a series of three papers, we have studied the formation and fate of such planetesimals formed at planetary gap edges. By performing global simulations of an evolving disk perturbed by multiple planets, and including a state-of-the-art dust evolution model, we find that planetesimals indeed should form at planetary gap edges, and in significant amounts. Furthermore, the described process has a dramatic impact on the evolution of solids in protoplanetary disks, and therefore also on how the disks appear in observations. We find that planets larger than the pebble isolation mass trap pebbles efficiently at the gap edges, and depending on the efficiency of planetesimal formation, the disk transforms to either a transition disk with a large inner hole devoid of dust or to a disk with narrow bright rings. When lower planetary masses are used, the result is a disk with a series of weak ring patterns.

By using gravitational N-body simulations we demonstrate that the close proximity between the planetesimals and the planets causes the planetesimals to leave their birth locations soon after formation and spread out across the disk. In the current paradigm of planet-disk interactions, planetary gaps are often invoked as a mechanism to separate the disk into an inner and outer part that do not exchange material, but our results show that scattered planetesimals can in fact carry material past these gaps. We further consider the accretion efficiency of these planetesimals onto the forming planets and show that it is very low, even in the most favorable cases. The high heavy element content of giant planets is often explained with planetesimal accretion during the gas accretion phase, but our results rather demonstrate that this is very unlikely. In conclusion, our work highlights that planetesimal formation at planetary gap edges can have huge implications for disk evolution and planet formation.
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author
supervisor
opponent
  • Associate Professor Zhu, Zhaohuan, University of Nevada, Las Vegas
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Protoplanetary disks, planet-disk interactions, planetesimal formation, planetesimal dynamics, giant planet formation
pages
132 pages
publisher
Lund Observatory, Lund University
defense location
Lundmarksalen, Astronomihuset, Sölvegatan 27, Lund, Sverige.
defense date
2022-05-13 13:00:00
ISBN
9789180391955
9789180391962
language
English
LU publication?
yes
id
b0bc4893-b91a-4d69-b084-3c9e0776848e
date added to LUP
2022-03-31 16:18:34
date last changed
2022-04-13 12:03:24
@phdthesis{b0bc4893-b91a-4d69-b084-3c9e0776848e,
  abstract     = {{High resolution observations with ALMA have revealed that concentric rings and gaps are common features in protoplanetary disks. The favored mechanism for creating these substructures are planet-disk interactions, in which growing planets open gaps in the disk, and particles become trapped at the pressure maxima that form at the corresponding gap edges. Since the particle density in these pressure bumps can become much higher than the global value, they are likely sites for planetesimal formation via the streaming instability. <br/><br/>In a series of three papers, we have studied the formation and fate of such planetesimals formed at planetary gap edges. By performing global simulations of an evolving disk perturbed by multiple planets, and including a state-of-the-art dust evolution model, we find that planetesimals indeed should form at planetary gap edges, and in significant amounts. Furthermore, the described process has a dramatic impact on the evolution of solids in protoplanetary disks, and therefore also on how the disks appear in observations. We find that planets larger than the pebble isolation mass trap pebbles efficiently at the gap edges, and depending on the efficiency of planetesimal formation, the disk transforms to either a transition disk with a large inner hole devoid of dust or to a disk with narrow bright rings. When lower planetary masses are used, the result is a disk with a series of weak ring patterns.<br/><br/>By using gravitational N-body simulations we demonstrate that the close proximity between the planetesimals and the planets causes the planetesimals to leave their birth locations soon after formation and spread out across the disk. In the current paradigm of planet-disk interactions, planetary gaps are often invoked as a mechanism to separate the disk into an inner and outer part that do not exchange material, but our results show that scattered planetesimals can in fact carry material past these gaps. We further consider the accretion efficiency of these planetesimals onto the forming planets and show that it is very low, even in the most favorable cases. The high heavy element content of giant planets is often explained with planetesimal accretion during the gas accretion phase, but our results rather demonstrate that this is very unlikely. In conclusion, our work highlights that planetesimal formation at planetary gap edges can have huge implications for disk evolution and planet formation.<br/>}},
  author       = {{Eriksson, Linn}},
  isbn         = {{9789180391955}},
  keywords     = {{Protoplanetary disks; planet-disk interactions; planetesimal formation; planetesimal dynamics; giant planet formation}},
  language     = {{eng}},
  publisher    = {{Lund Observatory, Lund University}},
  school       = {{Lund University}},
  title        = {{The formation and fate of planetesimals at planetary gap edges}},
  url          = {{https://lup.lub.lu.se/search/files/116093106/Avhandling_Linn_HELA.pdf}},
  year         = {{2022}},
}