Combined effects of disc winds and turbulence-driven accretion on planet populations

Alessi, Matthew

doi:10.1093/mnras/stac1782

“…Then, the authors study the effects of the discs initial properties (Alessi et al, 2020b) and the predictions on core and envelope composition (Alessi et al, 2020a). Their latest work focuses on the inclusion of magnetised disc winds as transport mechanism (Alessi and Pudritz, 2022).…”

Section: History and The Different Modelsmentioning

confidence: 99%

Planetary population synthesis and the emergence of four classes of planetary system architectures

Emsenhuber

¹

,

Mordasini

²

,

Burn

³

2023

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Planetary population synthesis is a helpful tool to understand the physics of planetary system formation. It builds on a global model, meaning that the model has to include a multitude of physical processes. The outcome can be statistically compared with exoplanet observations. Here, we review the population synthesis method and then use one population computed using the Generation III Bern model to explore how different planetary system architectures emerge and which conditions lead to their formation. The emerging systems can be classified into four main architectures: Class I of near in situ compositionally ordered terrestrial and ice planets, Class II of migrated sub-Neptunes, Class III of mixed low-mass and giant planets, broadly similar to the Solar System, and Class IV of dynamically active giants without inner low-mass planets. These four classes exhibit distinct typical formation pathways and are characterised by certain mass scales. We find that Class I forms from the local accretion of planetesimals followed by a giant impact phase, and the final planet masses correspond to what is expected from such a scenario, the ‘Goldreich mass’. Class II, the migrated sub-Neptune systems form when planets reach the ‘equality mass’ where accretion and migration timescales are comparable before the dispersal of the gas disc, but not large enough to allow for rapid gas accretion. Giant planets form when the ‘equality mass’ allows for gas accretion to proceed while the planet is migrating, i.e. when the critical core mass is reached. The main discriminant of the four classes is the initial mass of solids in the disc, with contributions from the lifetime and mass of the gas disc. The distinction between mixed Class III systems and Class IV dynamically active giants is in part due to the stochastic nature of dynamical interactions, such as scatterings between giant planets, rather than the initial conditions only. The breakdown of system into classes allows to better interpret the outcome of a complex model and understand which physical processes are dominant. Comparison with observations reveals differences to the actual population, pointing at limitation of theoretical understanding. For example, the overrepresentation of synthetic super-Earths and sub-Neptunes in Class I systems causes these planets to be found at lower metallicities than in observations.

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“…Conversely, if angular momentum is extracted by MHD winds, expansion is not required (Armitage et al 2013;Bai 2016;Tabone et al 2022; although see Yang & Bai 2021 for the possibility of wind-driven disks growing over time). It is worth mentioning that both processes could affect different parts of the disk simultaneously, thereby complicating our simple view of disk evolution (e.g., Alessi & Pudritz 2022). Other mechanisms such as the presence of a stellar companion (e.g., Papaloizou & Pringle 1977;Artymowicz & Lubow 1994;Zagaria et al 2021Zagaria et al , 2023b, external photoevaporation (e.g., Clarke 2007;Facchini et al 2016;Haworth et al 2018;Sellek et al 2020;Winter & Haworth 2022), and, if the disk size is determined from the dust continuum emission at submillimeter wavelengths, radial drift (Weidenschilling 1977;Rosotti et al 2019) can reduce the size of a protoplanetary disk and make it smaller with time, which has important consequences for disk evolution.…”

Section: Introductionmentioning

confidence: 99%

How Large Is a Disk—What Do Protoplanetary Disk Gas Sizes Really Mean?

Trapman,

Rosotti,

Zhang

et al. 2023

ApJ

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It remains unclear what mechanism is driving the evolution of protoplanetary disks. Direct detection of the main candidates, either turbulence driven by magnetorotational instabilities or magnetohydrodynamical disk winds, has proven difficult, leaving the time evolution of the disk size as one of the most promising observables able to differentiate between these two mechanisms. But to do so successfully, we need to understand what the observed gas disk size actually traces. We studied the relation between R CO,90%, the radius that encloses 90% of the 12CO flux, and R c , the radius that encodes the physical disk size, in order to provide simple prescriptions for conversions between these two sizes. For an extensive grid of thermochemical models, we calculate R CO,90% from synthetic observations and relate properties measured at this radius, such as the gas column density, to bulk disk properties, such as R c and the disk mass M disk. We found an empirical correlation between the gas column density at R CO,90% and disk mass: N gas ( R CO , 90 % ) ≈ 3.73 × 10 21 ( M disk / M ⊙ ) 0.34 cm − 2 . Using this correlation we derive an analytical prescription of R CO,90% that only depends on R c and M disk. We derive R c for disks in Lupus, Upper Sco, Taurus, and the DSHARP sample, finding that disks in the older Upper Sco region are significantly smaller (〈R c 〉 = 4.8 au) than disks in the younger Lupus and Taurus regions (〈R c 〉 = 19.8 and 20.9 au, respectively). This temporal decrease in R c goes against predictions of both viscous and wind-driven evolution, but could be a sign of significant external photoevaporation truncating disks in Upper Sco.

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A question of personalities: evolution of viscous and wind-driven protoplanetary discs in the presence of dead zones

Tong,

Alexander,

Rosotti

2024

Monthly Notices of the Royal Astronomical Society

0

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Whether the angular momentum of protoplanetary discs is redistributed by viscosity or extracted by magnetised winds is a long-standing question. Demographic indicators, such as gas disc sizes and stellar accretion rates, have been proposed as ways of distinguishing between these two mechanisms. In this paper, we implement one-dimensional gas simulations to study the evolution of “hybrid” protoplanetary discs simultaneously driven by viscosity and magnetised winds, with dead zones present. We explore how the variations of disc properties, including initial disc sizes, dead zone sizes and angular momentum transport efficiency, affect stellar accretion rates, disc surface density profiles, disc sizes, disc lifetimes, and cumulative mass loss by different processes. Our models show that the expansion of the gas disc size can be sustained when the majority of angular momentum is removed by the magnetised wind for individual protoplanetary discs. However, when we can only observe discs via demographic screenshots, the variation of disc sizes with time is possibly diminished by the disc ‘personalities’, by which we mean the variations of initial disc properties among different discs. Our ‘hybrid’ models re-assess association of the two demographic indicators with mechanisms responsible for angular momentum transport and suggest additional diagnostics are required to assist the differentiation.

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Combined effects of disc winds and turbulence-driven accretion on planet populations

Cited by 5 publications

References 157 publications

Planetary population synthesis and the emergence of four classes of planetary system architectures

Planetary population synthesis and the emergence of four classes of planetary system architectures

How Large Is a Disk—What Do Protoplanetary Disk Gas Sizes Really Mean?

A question of personalities: evolution of viscous and wind-driven protoplanetary discs in the presence of dead zones

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