Including Dust Coagulation in Hydrodynamic Models of Protoplanetary Disks: Dust Evolution in the Vicinity of a Jupiter-mass Planet

Aims. We explore the long-term evolution of young protoplanetary disks with different approaches to computing the thermal structure determined by various cooling and heating processes in the disk and its surroundings. Methods. Numerical hydrodynamics simulations in the thin-disk limit were complemented with three thermal evolution schemes: a simplified β-cooling approach with and without irradiation, where the rate of disk cooling is proportional to the local dynamical time; a fiducial model with equal dust and gas temperatures calculated taking viscous heating, irradiation, and radiative cooling into account; and a more sophisticated approach allowing decoupled dust and gas temperatures. Results. We found that the gas temperature may significantly exceed that of dust in the outer regions of young disks thanks to additional compressional heating caused by the infalling envelope material in the early stages of disk evolution and slow collisional exchange of energy between gas and dust in low-density disk regions. However, the outer envelope shows an inverse trend, with the gas temperatures dropping below that of dust. The global disk evolution is only weakly sensitive to temperature decoupling. Nevertheless, separate dust and gas temperatures may affect the chemical composition, dust evolution, and disk mass estimates. Constant-β models without stellar and background irradiation fail to reproduce the disk evolution with more sophisticated thermal schemes because of the intrinsically variable nature of the β-parameter. Constant-β models with irradiation more closely match the dynamical and thermal evolution, but the agreement is still incomplete. Conclusions. Models allowing separate dust and gas temperatures are needed when emphasis is placed on the chemical or dust evolution in protoplanetary disks, particularly in subsolar metallicity environments.

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Effects of Dust Evolution on the Vertical Shear Instability in the Outer Regions of Protoplanetary Disks

The Astrophysical Journal ◽

10.3847/1538-4357/abfe5c ◽

2021 ◽

Vol 914 (2) ◽

pp. 132

Author(s):

Yuya Fukuhara ◽

Satoshi Okuzumi ◽

Tomohiro Ono

Keyword(s):

Protoplanetary Disks ◽

Shear Instability ◽

Vertical Shear ◽

Dust Evolution

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Self-consistent Ring Model in Protoplanetary Disks: Temperature Dips and Substructure Formation

The Astrophysical Journal ◽

10.3847/1538-4357/ac2c82 ◽

2021 ◽

Vol 923 (1) ◽

pp. 70

Author(s):

Shangjia Zhang ◽

Xiao Hu ◽

Zhaohuan Zhu ◽

Jaehan Bae

Keyword(s):

Aerodynamic Drag ◽

Thermal Structure ◽

Protoplanetary Disks ◽

Dust Concentration ◽

Ring Model ◽

Self Consistent ◽

Shadowing Effect ◽

Set Up ◽

Dust Distribution ◽

Dust Evolution

Abstract Rings and gaps are ubiquitous in protoplanetary disks. Larger dust grains will concentrate in gaseous rings more compactly due to stronger aerodynamic drag. However, the effects of dust concentration on the ring’s thermal structure have not been explored. Using MCRT simulations, we self-consistently construct ring models by iterating the ring’s thermal structure, hydrostatic equilibrium, and dust concentration. We set up rings with two dust populations having different settling and radial concentration due to their different sizes. We find two mechanisms that can lead to temperature dips around the ring. When the disk is optically thick, the temperature drops outside the ring, which is the shadowing effect found in previous studies adopting a single-dust population in the disk. When the disk is optically thin, a second mechanism due to excess cooling of big grains is found. Big grains cool more efficiently, which leads to a moderate temperature dip within the ring where big dust resides. This dip is close to the center of the ring. Such a temperature dip within the ring can lead to particle pileup outside the ring and feedback to the dust distribution and thermal structure. We couple the MCRT calculations with a 1D dust evolution model and show that the ring evolves to a different shape and may even separate to several rings. Overall, dust concentration within rings has moderate effects on the disk’s thermal structure, and a self-consistent model is crucial not only for protoplanetary disk observations but also for planetesimal and planet formation studies.

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Elementary Composite Binary and Grain Alignment Locked in Dust Growth

The Astrophysical Journal ◽

10.3847/2041-8213/ac391e ◽

2021 ◽

Vol 923 (1) ◽

pp. L4

Author(s):

Z. W. Hu ◽

R. P. Winarski

Keyword(s):

Phase Contrast ◽

Protoplanetary Disks ◽

Interstellar Cloud ◽

Dust Grains ◽

Mantle Structure ◽

Grain Alignment ◽

X Ray ◽

Interstellar Grains ◽

Dust Evolution ◽

Octahedral Nanocrystals

Abstract Planets are known to grow out of a star-encircling disk of the gas and dust inherited from an interstellar cloud; their formation is thought to begin with coagulation of submicron dust grains into aggregates, the first foundational stage of planet formation. However, with nanoscale and submicron solids unobservable directly in the interstellar medium (ISM) and protoplanetary disks, how dust grains grow is unclear, as are the morphology and structure of interstellar grains and the whereabouts and form of “missing iron.” Here we show an elementary composite binary in 3D sub-10 nm detail—and the alignments of its two subunits and nanoinclusions and a population of elongated composite grains locked in a primitive cosmic dust particle—noninvasively uncovered with phase-contrast X-ray nanotomography. The binary comprises a pair of oblate, quasi-spheroidal grains whose alignment and shape meet the astrophysical constraints on polarizing interstellar grains. Each member of the pair contains a high-density core of octahedral nanocrystals whose twin relationship is consistent with the magnetite’s diagnostic property at low temperatures, with a mantle exhibiting nanoscale heterogeneities, rounded edges, and pitted surfaces. This elongated binary evidently formed from an axially aligned collision of the two similar composite grains whose core–mantle structure and density gradients are consistent with interstellar processes and astronomical evidence for differential depletion. Our findings suggest that the ISM is threaded with dust grains containing preferentially oriented iron-rich magnetic nanocrystals that hold answers to astronomical problems from dust evolution, grain alignment, and the structure of magnetic fields to planetesimal growth.

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Molecular Hydrogen Emission from Protoplanetary Disks. II. Effects of X‐Ray Irradiation and Dust Evolution

The Astrophysical Journal ◽

10.1086/513419 ◽

2007 ◽

Vol 661 (1) ◽

pp. 334-353 ◽

Cited By ~ 112

Author(s):

H. Nomura ◽

Y. Aikawa ◽

M. Tsujimoto ◽

Y. Nakagawa ◽

T. J. Millar

Keyword(s):

Molecular Hydrogen ◽

Protoplanetary Disks ◽

X Ray ◽

Hydrogen Emission ◽

Dust Evolution

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A Mid-Infrared Study of Dust Evolution: Protoplanetary Disks, Circumstellar Envelopes, and Lmircam Development

10.18130/v3h87c ◽

2011 ◽

Author(s):

Jarron Michael Leisenring

Keyword(s):

Protoplanetary Disks ◽

Circumstellar Envelopes ◽

Infrared Study ◽

Mid Infrared ◽

Dust Evolution

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Hints on the origins of particle traps in protoplanetary disks given by the Mdust – M⋆ relation

Astronomy and Astrophysics ◽

10.1051/0004-6361/201937003 ◽

2020 ◽

Vol 635 ◽

pp. A105 ◽

Cited By ~ 6

Author(s):

Paola Pinilla ◽

Ilaria Pascucci ◽

Sebastian Marino

Keyword(s):

Giant Planet ◽

Protoplanetary Disks ◽

Stellar Mass ◽

Dust Particles ◽

Low Mass Stars ◽

Dust Trapping ◽

Star Forming ◽

Star Forming Regions ◽

Demographic Surveys ◽

Dust Evolution

Context. Demographic surveys of protoplanetary disks, carried out mainly with the Atacama Large Millimeter/submillimete Array, have provided access to a large range of disk dust masses (Mdust) around stars with different stellar types and in different star-forming regions. These surveys found a power-law relation between Mdust and M⋆ that steepens in time, but which is also flatter for transition disks (TDs). Aims. We aim to study the effect of dust evolution in the Mdust−M⋆ relation. In particular, we are interested in investigating the effect of particle traps on this relation. Methods. We performed dust evolution models, which included perturbations to the gas surface density with different amplitudes to investigate the effect of particle trapping on the Mdust−M⋆ relation. These perturbations were aimed at mimicking pressure bumps that originated from planets. We focused on the effect caused by different stellar and disk masses based on exoplanet statistics that demonstrate a dependence of planet mass on stellar mass and metallicity. Results. Models of dust evolution can reproduce the observed Mdust−M⋆ relation in different star-forming regions when strong pressure bumps are included and when the disk mass scales with stellar mass (case of Mdisk = 0.05 M⋆ in our models). This result arises from dust trapping and dust growth beyond centimeter-sized grains inside pressure bumps. However, the flatter relation of Mdust − M⋆ for TDs and disks with substructures cannot be reproduced by the models unless the formation of boulders is inhibited inside pressure bumps. Conclusions. In the context of pressure bumps originating from planets, our results agree with current exoplanet statistics on giant planet occurrence increasing with stellar mass, but we cannot draw a conclusion about the type of planets needed in the case of low-mass stars. This is attributed to the fact that for M⋆ < 1 M⊙, the observed Mdust obtained from models is very low due to the efficient growth of dust particles beyond centimeter-sizes inside pressure bumps.

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