Outward Migration of Super-Jupiters

Dempsey, Adam M.; Muñoz, Diego J.; Lithwick, Yoram

doi:10.48550/arxiv.2105.05277

Cited by 4 publications

(15 citation statements)

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“…This is in excellent agreement with the picture painted by van der Marel & Mulders (2021) which hinges on the assumption that ring/gap-creating planets will eventually migrate inward again. On another note, outward migration of Super-Jupiter planets has also been reported in simulations of low viscosity disks (Dempsey et al 2021).…”

Section: Discussionsupporting

confidence: 53%

Turbulent disc viscosity and the bifurcation of planet formation histories

Speedie

Cridland

Meru

et al. 2021

Monthly Notices of the Royal Astronomical Society

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ALMA observations of dust ring/gap structures in a minority but growing sample of protoplanetary disks can be explained by the presence of planets at large disk radii - yet the origins of these planets remains debated. We perform planet formation simulations using a semi-analytic model of the HL Tau disk to follow the growth and migration of hundreds of planetary embryos initially distributed throughout the disk, assuming either a high or low turbulent α viscosity. We have discovered that there is a bifurcation in the migration history of forming planets as a consequence of varying the disk viscosity. In our high viscosity disks, inward migration prevails and yields compact planetary systems, tempered only by planet trapping at the water iceline around 5 au. In our lower viscosity models however, low mass planets can migrate outward to twice their initial orbital radii, driven by a radially extended region of strong outward-directed corotation torques located near the heat transition (where radiative heating of the disk by the star is comparable to viscous heating) - before eventually migrating inwards. We derive analytic expressions for the planet mass at which the corotation torque dominates, and find that this “corotation mass” scales as Mp, corot ∼ α2/3. If disk winds dominate the corotation torque, the corotation mass scales linearly with wind strength. We propose that the observed bifurcation in disk demographics into a majority of compact dust disks and a minority of extended ring/gap systems is a consequence of a distribution of viscosity across the disk population.

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Section: Discussionsupporting

confidence: 53%

Turbulent disc viscosity and the bifurcation of planet formation histories

Speedie

Cridland

Meru

et al. 2021

Monthly Notices of the Royal Astronomical Society

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“…Under especial circumstances, single massive planets can also migrate outwards (e.g. Masset & Papaloizou 2003;Crida & Morbidelli 2007;Pepliński et al 2008;Lin & Papaloizou 2012;Dempsey et al 2021), although these cases might be inconsistent with our assumption of an axisymmetric disc. It could also be the case that the dust traps are caused by mechanisms that do not involve the presence of planets, and that these could migrate as discs evolve.…”

Section: Outward Migrating Dust Trapmentioning

confidence: 72%

The formation of wide exoKuiper belts from migrating dust traps

Miller,

Marino,

Stammler

et al. 2021

Preprint

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The question of what determines the width of Kuiper belt analogues (exoKuiper belts) is an open one. If solved, this understanding would provide valuable insights into the architecture, dynamics, and formation of exoplanetary systems. Recent observations by ALMA have revealed an apparent paradox in this field, the presence of radially narrow belts in protoplanetary discs that are likely the birthplaces of planetesimals, and exoKuiper belts nearly four times as wide in mature systems. If the parent planetesimals of this type of debris disc indeed form in these narrow protoplanetary rings via streaming instability where dust is trapped, we propose that this width dichotomy could naturally arise if these dust traps form planetesimals whilst migrating radially, e.g. as caused by a migrating planet. Using the dust evolution software D P , we find that if the initial protoplanetary disc and trap conditions favour planetesimal formation, dust can still effectively accumulate and form planetesimals as the trap moves. This leads to a positive correlation between the inward radial speed and final planetesimal belt width, forming belts up to ∼100 au over 10 Myr of evolution. We show that although planetesimal formation is most efficient in low viscosity (𝛼 = 10 −4 ) discs with steep dust traps to trigger the streaming instability, the large widths of most observed planetesimal belts constrain 𝛼 to values ≥ 4 × 10 −4 at tens of au, otherwise the traps cannot migrate far enough. Additionally, the large spread in the widths and radii of exoKuiper belts could be due to different trap migration speeds (or protoplanetary disc lifetimes) and different starting locations, respectively. Our work serves as a first step to link exoKuiper belts and rings in protoplanetary discs.

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“…The parameter 𝐾 ′ has been empirically studied by Kanagawa et al (2016Kanagawa et al ( , 2018 and by Dempsey et al (2020Dempsey et al ( , 2021, who noticed that 𝐾 ′ correlates with the gap width and depth (with the gap becoming wider and deeper for higher 𝐾 ′ values). Systems characterised by the same 𝐾 ′ also appear to show similar torque density profiles; thus Dempsey et al (2020Dempsey et al ( , 2021 examined a number of fixed-planet 2 simulations characterised by different 𝐾 ′ values, and suggested that 𝐾 ′ is a good 'ordering parameter' for planet migration. According to their analysis, in fact, planets in systems characterised by 𝐾 ′ ≳ 20 migrate outward, whereas systems with 𝐾 ′ ≲ 20 present inward planet migration.…”

Section: Dependence On Initial Disc Massmentioning

confidence: 99%

“…Further investigation on the planet migration direction has been recently conducted by Dempsey et al (2020Dempsey et al ( , 2021, who used a set of 2D systems in the planet-dominated regime, in a stable steady state condition. To study planet migration they model the situation where the planet's orbital parameters (semi-major axis and eccentricity) are not allowed to evolve; they then calculate planet migration from the torques acting on the fixed planet.…”

Section: Introductionmentioning

confidence: 99%

“…In this paper, we present a suite of 2D simulations lasting ≳ 300k orbits, for a variety of aspect ratios 𝐻/𝑟, planet masses 𝑀 𝑝 and disc masses 𝑀 disc . These simulations are intended to be complementary to those by Dempsey et al (2021), and allow us to investigate both the importance or otherwise of employing a 'live' planet, as well as the role of different boundary conditions. Since these simulations are extremely expensive from the computational point of view, such simulations have never been performed before; consequently this is a new area of exploration for the disc-planet interaction problem, and the present simulation set inevitably leaves some questions unanswered.…”

Section: Introductionmentioning

confidence: 99%

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Inward and outward migration of massive planets: moving towards a stalling radius

Scardoni

Clarke

Rosotti

et al. 2022

Monthly Notices of the Royal Astronomical Society

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Recent studies on the planet-dominated regime of Type II migration showed that, contrary to the conventional wisdom, massive planets can migrate outwards. Using ‘fixed-planet’ simulations these studies found a correlation between the sign of the torques acting on the planet and the parameter K′ (which describes the depth of the gap carved by the planet in the disc). We perform ‘live-planet’ simulations exploring a range of K′ and disc mass values to test and extend these results. The excitation of planet eccentricity in live-planet simulations breaks the direct dependence of migration rate (rate of change of semi-major axis) on the torques imposed, an effect that ‘fixed-planet’ simulations cannot treat. By disentangling the contribution to the torque due to the semi-major axis evolution from that due to the eccentricity evolution, we recover the relation between the magnitude and sign of migration and K′ and argue that this relation may be better expressed in terms of the related gap depth parameter K. We present a toy model in which the sign of planetary migration changes at a limiting value of K, through which we explore planets’ migration in viscously evolving discs. The existence of the torque reversal shapes the planetary system’s architecture by accumulating planets either at the stalling radius or in a band around it (defined by the interplay between the planet migration and the disc evolution). In either case, planets pile up in the area 1 − 10 au, disfavouring hot Jupiter formation through Type II migration in the planet-dominated regime.

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Outward Migration of Super-Jupiters

Cited by 4 publications

References 0 publications

Turbulent disc viscosity and the bifurcation of planet formation histories

Turbulent disc viscosity and the bifurcation of planet formation histories

The formation of wide exoKuiper belts from migrating dust traps

Inward and outward migration of massive planets: moving towards a stalling radius

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