On the formation of compact planetary systems via concurrent core accretion and migration

Coleman, Gavin A. L.; Nelson, Richard P.

doi:10.1093/mnras/stw149

Cited by 97 publications

(112 citation statements)

References 81 publications

(122 reference statements)

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“…The formation of such resonant chains are a natural outcome of interactions between the planets and their nascent protoplanetary discs (Cresswell & Nelson 2008). These resonant chains have been observed in other compact planetary systems (Lissauer et al 2011;Fabrycky et al 2014;Mills et al 2016), and have also been formed in complex planet formation simulations involving multiple bodies (Hellary & Nelson 2012;Coleman & Nelson 2014, 2016b. Whilst Trappist-1 may be the most high-profile planetary system around low mass stars, it is interesting to note that a number of similar planetary systems have also been recently observed.…”

Section: Introductionmentioning

confidence: 87%

Pebbles versus planetesimals: the case of Trappist-1

Coleman

Leleu

Alibert

et al. 2019

A&A

107

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We present a study into the formation of planetary systems around low mass stars similar to Trappist-1, through the accretion of either planetesimals or pebbles. The aim is to determine if the currently observed systems around low mass stars could favour one scenario over the other. To determine these differences, we ran numerous N-body simulations, coupled to a thermally evolving viscous 1D disc model, and including prescriptions for planet migration, photoevaporation, and pebble and planetesimal dynamics. We mainly examine the differences between the pebble and planetesimal accretion scenarios, but we also look at the influences of disc mass, size of planetesimals, and the percentage of solids locked up within pebbles. When comparing the resulting planetary systems to Trappist-1, we find that a wide range of initial conditions for both the pebble and planetesimal accretion scenarios can form planetary systems similar to Trappist-1, in terms of planet mass, periods, and resonant configurations. Typically these planets formed exterior to the water iceline and migrated in resonant convoys into the inner region close to the central star. When comparing the planetary systems formed through pebble accretion to those formed through planetesimal accretion, we find a large number of similarities, including average planet masses, eccentricities, inclinations and period ratios. One major difference between the two scenarios was that of the water content of the planets. When including the effects of ablation and full recycling of the planets' envelope with the disc, the planets formed through pebble accretion were extremely dry, whilst those formed through planetesimal accretion were extremely wet. If the water content is not fully recycled and instead falls to the planets' core, or if ablation of the water is neglected, then the planets formed through pebble accretion are extremely wet, similar to those formed through planetesimal accretion. Should the water content of the Trappist-1 planets be determined accurately, this could point to a preferred formation pathway for planetary systems, or to specific physics that may be at play.

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Section: Introductionmentioning

confidence: 87%

Pebbles versus planetesimals: the case of Trappist-1

Coleman

Leleu

Alibert

et al. 2019

A&A

107

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“…These regions, where the positive corotation torque balances the negative Lindblad torque, are radii of net torque equilibrium, referred to as planet traps. Numerical works, such as Lyra et al (2010) and Coleman & Nelson (2016a) have calculated the sense of migration of orbits near planet traps and have shown traps to be stable equilibria, and as such nearby orbits will migrate towards planet traps. Inhomogeneities and transitions in disks are therefore likely sites of planet formation.…”

Section: Appendix B: Planet Migration and Formationmentioning

confidence: 99%

“…Other works that have computed type-I torques on a range of planet masses and disk radii for various disk models (so-called migration maps) have shown zero net torque locations to be common (Hellary & Nelson 2012;Baillié et al 2016;Coleman & Nelson 2016a;Cridland et al 2019). However, these works find that the locations of the equilibrium points have mass dependences.…”

Section: Appendix B: Planet Migration and Formationmentioning

confidence: 99%

Formation of planetary populations − II. Effects of initial disc size and radial dust drift

Alessi

Cridland

2020

Monthly Notices of the Royal Astronomical Society

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Recent ALMA observations indicate that while a range of disk sizes exist, typical disk radii are small, and that radial dust drift affects the distribution of solids in disks.Here we explore the consequences of these features in planet population synthesis models. A key feature of our model is planet traps -barriers to otherwise rapid type-I migration of forming planets -for which we include the ice line, heat transition, and outer edge of the dead zone. We find that the ice line plays a fundamental role in the formation of warm Jupiters. In particular, the ratio of super Earths to warm Jupiters formed at the ice line depend sensitively on the initial disk radius. Initial gas disk radii of ∼50 AU results in the largest super Earth populations, while both larger and smaller disk sizes result in the ice line producing more gas giants near 1 AU. This transition between typical planet class formed at the ice line at various disk radii confirms that planet formation is fundamentally linked to disk properties (in this case, disk size), and is a result that is only seen when dust evolution effects are included in our models. Additionally, we find that including radial dust drift results in the formation of more super Earths between 0.1 -1 AU, having shorter orbital radii than those produced in models where dust evolution effects are not included.

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“…On top of that, Type II migration rate is still under debate, as some recent simulations find that it is independent of the disk viscous flow rate (Duffell et al 2014;Dürmann & Kley 2015). Another way to stop fast migration is to invoke planet traps (e.g., Hasegawa & Pudritz 2011;Bitsch et al 2015;Coleman & Nelson 2016a, 2016bBrasser et al 2017)-points in disks where the local temperature and density gradients generate corotation torques that exactly balance the Lindblad torques on the planets. To sustain the corotation torque, viscous diffusion in the disk needs to be on a level of α10 −3 for super-Earths near 1au (Masset & Casoli 2010;Paardekooper et al 2011), where α is the Shakura-Sunyaev parameter (Shakura & Sunyaev 1973).…”

Section: Introductionmentioning

confidence: 99%

Inner Super-Earths, Outer Gas Giants: How Pebble Isolation and Migration Feedback Keep Jupiters Cold

Fung

Lee

2018

ApJ

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The majority of gas giants (planets of masses 10 2 M ⊕ ) are found to reside at distances beyond ∼1 au from their host stars. Within 1 au, the planetary population is dominated by super-Earths of 2-20M ⊕ . We show that this dichotomy between inner super-Earths and outer gas giants can be naturally explained should they form in nearly inviscid disks. In laminar disks, a planet can more easily repel disk gas away from its orbit. The feedback torque from the pile-up of gas inside the planet's orbit slows down and eventually halts migration. A pressure bump outside the planet's orbit traps pebbles and solids, starving the core. Gas giants are born cold and stay cold: more massive cores are preferentially formed at larger distances, and they barely migrate under disk feedback. We demonstrate this using two-dimensional hydrodynamical simulations of disk-planet interaction lasting up to 10 5 years: we track planet migration and pebble accretion until both come to an end by disk feedback. Whether cores undergo runaway gas accretion to become gas giants or not is determined by computing one-dimensional gas accretion models. Our simulations show that in an inviscid minimum mass solar nebula, gas giants do not form inside ∼0.5au, nor can they migrate there while the disk is present. We also explore the dependence on disk mass and find that gas giants form further out in less massive disks.

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On the formation of compact planetary systems via concurrent core accretion and migration

Cited by 97 publications

References 81 publications

Pebbles versus planetesimals: the case of Trappist-1

Pebbles versus planetesimals: the case of Trappist-1

Formation of planetary populations − II. Effects of initial disc size and radial dust drift

Inner Super-Earths, Outer Gas Giants: How Pebble Isolation and Migration Feedback Keep Jupiters Cold

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