scholarly journals Gravitoviscous protoplanetary disks with a dust component

2019 ◽  
Vol 627 ◽  
pp. A154 ◽  
Author(s):  
Eduard I. Vorobyov ◽  
Aleksandr M. Skliarevskii ◽  
Vardan G. Elbakyan ◽  
Yaroslav Pavlyuchenkov ◽  
Vitaly Akimkin ◽  
...  
Keyword(s):  
Mass Transport ◽  
Gravitational Instability ◽  
Protoplanetary Disks ◽  
Circumstellar Disks ◽  
Appreciable Effect ◽  
Streaming Instability ◽  
T Tauri ◽  
Dust Component ◽  
Cloud Cores ◽  
Slow Transport

Aims. The central region of a circumstellar disk is difficult to resolve in global numerical simulations of collapsing cloud cores, but its effect on the evolution of the entire disk can be significant. Methods. We used numerical hydrodynamics simulations to model the long-term evolution of self-gravitating and viscous circumstellar disks in the thin-disk limit. Simulations start from the gravitational collapse of pre-stellar cores of 0.5–1.0 M⊙ and both gaseous and dusty subsystems were considered, including a model for dust growth. The inner unresolved 1.0 au of the disk is replaced with a central smart cell (CSC), a simplified model that simulates physical processes that may occur in this region. Results. We found that the mass transport rate through the CSC has an appreciable effect on the evolution of the entire disk. Models with slow mass transport form more massive and warmer disks, and are more susceptible to gravitational instability and fragmentation, including a newly identified episodic mode of disk fragmentation in the T Tauri phase of disk evolution. Models with slow mass transport through the CSC feature episodic accretion and luminosity bursts in the early evolution, while models with fast transport are characterized by a steadily declining accretion rate with low-amplitude flickering. Dust grows to a larger, decimeter size in the slow transport models and efficiently drifts in the CSC, where it accumulates and reaches the limit where a streaming instability becomes operational. We argue that gravitational instability, together with a streaming instability likely operating in the inner disk regions, constitute two concurrent planet-forming mechanisms, which may explain the observed diversity of exoplanetary orbits. Conclusions. We conclude that sophisticated models of the inner unresolved disk regions should be used when modeling the formation and evolution of gaseous and dusty protoplanetary disks.

scholarly journals The Nobeyama Millimeter Array Survey for Protoplanetary Disks Around Protostar Candidates and T Tauri Stars in Taurus

1994 ◽  
Vol 140 ◽  
pp. 274-275
Author(s):  
Nagayoshi Ohashi ◽  
Ryohei Kawabe ◽  
Masahiko Hayashi ◽  
Masato Ishiguro
Keyword(s):  
Protoplanetary Disks ◽  
Circumstellar Disks ◽  
Stellar Mass ◽  
T Tauri Stars ◽  
Continuum Emission ◽  
Disk Mass ◽  
T Tauri ◽  
The Continuum

AbstractThe Nobeyama Millimeter Array Survey for protoplanetary disks has been made for 19 protostellar IRAS sources in Taurus; 13 were invisible protostars and 6 were youngest T Tauri stars. We observed the 98 GHz continuum and CS(J=2-1) line emissions simultaneously with spatial resolutions of 2.8”- 8.8” (360 AU-1,200 AU). Unresolved continuum emission was detected from 5 of 6 T Tauri stars and 2 of 13 protostar candidates. The continuum emission arose from compact circumstellar disks. Extended CS emission was detected around 2 T Tauri stars and 11 protostar candidates. There is a remarkable tendency for the detectability for the 98 GHz continuum emission to be small for protostar candidates. This tendency is explained if the mass of protoplanetary disks around protostars is not as large as that around T Tauri stars; the disk mass may increase with the increase of central stellar mass by dynamical accretion in the course of evolution from protostars to T Tauri stars.

scholarly journals Early evolution of viscous and self-gravitating circumstellar disks with a dust component

2018 ◽  
Vol 614 ◽  
pp. A98 ◽  
Author(s):  
Eduard I. Vorobyov ◽  
Vitaly Akimkin ◽  
Olga Stoyanovskaya ◽  
Yaroslav Pavlyuchenkov ◽  
Hauyu Baobab Liu
Keyword(s):  
Radial Distance ◽  
Circumstellar Disks ◽  
Growth Efficiency ◽  
Azimuthal Velocity ◽  
Narrow Region ◽  
Numerical Hydrodynamics ◽  
T Tauri ◽  
Dust Component ◽  
Disk Evolution ◽  
Self Gravity

Context. Aims. The long-term evolution of a circumstellar disk starting from its formation and ending in the T Tauri phase was simulated numerically with the purpose of studying the evolution of dust in the disk with distinct values of the viscous α-parameter and dust fragmentation velocity vfrag. Methods. We solved numerical hydrodynamics equations in the thin-disk limit, which were modified to include a dust component consisting of two parts: sub-micron-sized dust, and grown dust with a maximum radius ar. The former is strictly coupled to the gas, while the latter interacts with the gas through friction. Dust growth, dust self-gravity, and the conversion of small to grown dust were also considered. Results. We found that the process of dust growth that is known for the older protoplanetary phase also holds for the embedded phase of the disk evolution. The dust growth efficiency depends on the radial distance from the star – ar is largest in the inner disk and gradually declines with radial distance. In the inner disk, ar is limited by the dust fragmentation barrier. The process of small-to-grown dust conversion is very fast once the disk is formed. The total mass of the grown dust in the disk (beyond 1 AU) reaches tens or even hundreds of Earth masses as soon as in the embedded phase of star formation, and an even greater amount of grown dust drifts in the inner, unresolved 1 AU of the disk. Dust does not usually grow to radii greater than a few cm. A notable exception are models with α ≤ 10−3, in which case a zone with reduced mass transport develops in the inner disk and dust can grow to meter-sized boulders in the inner 10 AU. Grown dust drifts inward and accumulates in the inner disk regions. This effect is most pronounced in the α ≤ 10−3 models, where several hundreds of Earth masses can be accumulated in a narrow region of several AU from the star by the end of embedded phase. The efficiency of grown dust accumulation in spiral arms is stronger near corotation where the azimuthal velocity of dust grains is closest to the local velocity of the spiral pattern. In the framework of the adopted dust growth model, the efficiency of small-to-grown dust conversion was found to increase for lower values of α and vfrag.

Astrochemical models of water

2015 ◽  
Vol 11 (A29B) ◽  
pp. 380-384
Author(s):  
Yuri Aikawa
Keyword(s):  
Molecular Clouds ◽  
Early Stage ◽  
Reaction Network ◽  
Network Models ◽  
Circumstellar Disks ◽  
Disk Surface ◽  
Water Ice ◽  
T Tauri ◽  
Deuterium Enrichment ◽  
Cloud Cores

AbstractWe will review the chemical reaction network models of water and its D/H ratio coupled with the dynamics of star formation. Infrared observations show that water ice is abundant even in molecular clouds with relatively low visual extinction (~ 3 mag), which indicates that water ice is formed in early stage of molecular clouds. We thus start from a possible formation site of molecular clouds, i.e. the converging flow of diffuse gas. Then we proceed to dense cloud cores and its gravitational collapse, during which a significant deuterium enrichment occurs. The gas and ice accrete onto the circumstellar disks, which evolve to protoplanetary disks in T Tauri phase. If the disks are turbulent, water could be photodissociated in the disk surface and re-formed in deeper layers. The cycle continues until the dust grains with ice mantle are decoupled from the turbulence and settle to the midplane. The water D/H ratio could thus vary within the disk.

scholarly journals Gravitoviscous protoplanetary disks with a dust component

2019 ◽  
Vol 631 ◽  
pp. A1 ◽  
Author(s):  
Eduard I. Vorobyov ◽  
Vardan G. Elbakyan
Keyword(s):  
Gravitational Instability ◽  
Protoplanetary Disks ◽  
Maximum Radius ◽  
Order Of Magnitude ◽  
Dust Component ◽  
Tidal Torques ◽  
Self Gravity ◽  
Small Dust ◽  
Collapse Phase ◽  
Hydrodynamics Equations

Aims. Spatial distribution and growth of dust in a clumpy protoplanetary disk subject to vigorous gravitational instability and fragmentation is studied numerically with sub-au resolution using the FEOSAD code. Methods. Hydrodynamics equations describing the evolution of self-gravitating and viscous protoplanetary disks in the thin-disk limit were modified to include a dust component consisting of two parts: sub-micron-sized dust and grown dust with a variable maximum radius. The conversion of small to grown dust, dust growth, friction of dust with gas, and dust self-gravity were also considered. Results. We found that the disk appearance is notably time-variable with spiral arms, dusty rings, and clumps, constantly forming, evolving, and decaying. As a consequence, the total dust-to-gas mass ratio is highly non-homogeneous throughout the disk extent, showing order-of-magnitude local deviations from the canonical 1:100 value. Gravitationally bound clumps formed through gravitational fragmentation have a velocity pattern that deviates notably from the Keplerian rotation. Small dust is efficiently converted into grown dust in the clump interiors, reaching a maximum radius of several decimeters. Concurrently, grown dust drifts towards the clump center forming a massive compact central condensation (70–100 M⊕). We argue that protoplanets may form in the interiors of inward-migrating clumps before they disperse through the action of tidal torques. We foresee the formation of protoplanets at orbital distances of several tens of au with initial masses of gas and dust in the protoplanetary seed in the (0.25–1.6) MJup and (1.0–5.5) M⊕ limits, respectively. The final masses of gas and dust in the protoplanets may however be much higher due to accretion from surrounding massive metal-rich disks/envelopes. Conclusions. Dusty rings formed through tidal dispersal of inward-migrating clumps may have a connection to ring-like structures found in youngest and massive protoplanetary disks. Numerical disk models with a dust component that can follow the evolution of gravitationally bound clumps through their collapse phase to the formation of protoplanets are needed to make firm conclusions on the characteristics of planets forming through gravitational fragmentation.

scholarly journals Gravitoviscous protoplanetary disks with a dust component

2020 ◽  
Vol 637 ◽  
pp. A5 ◽  
Author(s):  
Vardan G. Elbakyan ◽  
Anders Johansen ◽  
Michiel Lambrechts ◽  
Vitaly Akimkin ◽  
Eduard I. Vorobyov
Keyword(s):  
Surface Density ◽  
Planet Formation ◽  
Gravitational Instability ◽  
Protoplanetary Disks ◽  
Dust Particles ◽  
Circumstellar Disk ◽  
Power Law Distribution ◽  
Momentum Exchange ◽  
Disk Formation ◽  
Dust Component

Aims. We study the dynamics and growth of dust particles in circumstellar disks of different masses that are prone to gravitational instability during the critical first Myr of their evolution. Methods. We solved the hydrodynamics equations for a self-gravitating and viscous circumstellar disk in a thin-disk limit using the FEOSAD numerical hydrodynamics code. The dust component is made up of two different components: micron-sized dust and grown dust of evolving size. For the dust component, we considered the dust coagulation, fragmentation, momentum exchange with the gas, and dust self-gravity. Results. We found that the micron-sized dust particles grow rapidly in the circumstellar disk, reaching a few cm in size in the inner 100 au of the disk during less than 100 kyr after the disk formation, provided that fragmentation velocity is 30 ms−1. Due to the accretion of micron dust particles from the surrounding envelope, which serves as a micron dust reservoir, the approximately cm-sized dust particles continue to be present in the disk for more than 900 kyr after the disk formation and maintain a dust-to-gas ratio close to 0.01. We show that a strong correlation exists between the gas and pebble fluxes in the disk. We find that radial surface density distribution of pebbles in the disk shows power-law distribution with an index similar to that of the Minimum-mass solar nebula regardless the disk mass. We also show that the gas surface density in our models agrees well with measurements of dust in protoplanetary disks of AS 209, HD 163296, and DoAr 25 systems. Conclusions. Pebbles are formed during the very early stages of protoplanetary disk evolution. They play a crucial role in the planet formation process. Our disc simulations reveal the early onset (<105 yr) of an inwards-drifting flux of pebble-sized particles that makes up approximately between one hundredth and one tenth of the gas mass flux, which appears consistent with mm-observations of discs. Such a pebble flux would allow for the formation of planetesimals by streaming instability and the early growth of embryos by pebble accretion. We conclude that unlike the more common studies of isolated steady-state protoplanetary disks, more sophisticated global numerical simulations of circumstellar disk formation and evolution, including the pebble formation from the micron dust particles, are needed for performing realistic planet formation studies.

The Infancy of Solar-Type Stars and its Relevance for the Origin of Life

1997 ◽  
Vol 161 ◽  
pp. 267-282 ◽  
Author(s):  
Thierry Montmerle
Keyword(s):  
Main Sequence ◽  
Solar Nebula ◽  
Circumstellar Disks ◽  
T Tauri Stars ◽  
Necessary Condition ◽  
Sequence Evolution ◽  
T Tauri ◽  
Solar Type ◽  
Optical Domain ◽  
The Origin Of Life

AbstractFor life to develop, planets are a necessary condition. Likewise, for planets to form, stars must be surrounded by circumstellar disks, at least some time during their pre-main sequence evolution. Much progress has been made recently in the study of young solar-like stars. In the optical domain, these stars are known as «T Tauri stars». A significant number show IR excess, and other phenomena indirectly suggesting the presence of circumstellar disks. The current wisdom is that there is an evolutionary sequence from protostars to T Tauri stars. This sequence is characterized by the initial presence of disks, with lifetimes ~ 1-10 Myr after the intial collapse of a dense envelope having given birth to a star. While they are present, about 30% of the disks have masses larger than the minimum solar nebula. Their disappearance may correspond to the growth of dust grains, followed by planetesimal and planet formation, but this is not yet demonstrated.

scholarly journals Aperture synthesis CS and 98 GHz continuum observations of protostellar IRAS sources in Taurus

1991 ◽  
Vol 147 ◽  
pp. 353-356
Author(s):  
N. Ohashi ◽  
R. Kawabe ◽  
M. Hayashi ◽  
M. Ishiguro
Keyword(s):  
Molecular Cloud ◽  
Total Mass ◽  
T Tauri Stars ◽  
Continuum Emission ◽  
Beam Size ◽  
Dust Grains ◽  
Dynamical Mass ◽  
T Tauri ◽  
Cloud Cores ◽  
The Continuum

The CS (J = 2 — 1) line and 98 GHz continuum emission have been observed for 11 protostellar IRAS sources in the Taurus molecular cloud with resolutions of 2.6″−8.8″ (360 AU—1200 AU) using the Nobeyama Millimeter Array (NMA). The CS emission is detected only toward embedded sources, while the continuum emission from dust grains is detected only toward visible T Tauri stars except for one embedded source, L1551-IRS5. This suggests that the dust grains around the embedded sources do not centrally concentrate enough to be detected with our sensitivity (∼4 m Jy r.m.s), while dust grains in disks around the T Tauri stars have enough total mass to be detected with the NMA. The molecular cloud cores around the embedded sources are moderately extended and dense enough to be detected in CS, while gas disks around the T Tauri are not detected because the radius of such gas disks may be smaller than 70 (50 K/Tex) AU. These results imply that the total amount of matter within the NMA beam size must increase when the central objects evolve into T Tauri stars from embedded sources, suggesting that the compact and highly dense disks around T Tauri stars are formed by the dynamical mass accretion during the embedded protostar phase.

scholarly journals A Lagrangian model for dust evolution in protoplanetary disks: formation of wet and dry planetesimals at different stellar masses

2018 ◽  
Vol 620 ◽  
pp. A134 ◽  
Author(s):  
Djoeke Schoonenberg ◽  
Chris W. Ormel ◽  
Sebastiaan Krijt
Keyword(s):  
Accretion Rate ◽  
Protoplanetary Disks ◽  
Particle Method ◽  
Solid Particles ◽  
Lagrangian Model ◽  
Low Mass Stars ◽  
Streaming Instability ◽  
Mass Fluxes ◽  
Gas Accretion ◽  
Stellar Masses

We introduce a new Lagrangian smooth-particle method to model the growth and drift of pebbles in protoplanetary disks. The Lagrangian nature of the model makes it especially suited to following characteristics of individual (groups of) particles, such as their composition. In this work we focus on the water content of solid particles. Planetesimal formation via streaming instability is taken into account, partly based on previous results on streaming instability outside the water snowline that were presented in a recent publication. We validated our model by reproducing earlier results from the literature and apply our model to steady-state viscous gas disks (with constant gas accretion rate) around stars with different masses. We also present various other models where we explore the effects of pebble accretion, the fragmentation velocity threshold, the global metallicity of the disk, and a time-dependent gas accretion rate. We find that planetesimals preferentially form in a local annulus outside the water snowline, at early times in the lifetime of the disk (≲105 yr), when the pebble mass fluxes are high enough to trigger the streaming instability. During this first phase in the planet formation process, the snowline location hardly changes due to slow viscous evolution, and we conclude that assuming a constant gas accretion rate is justified in this first stage. The efficiency of converting the solids reservoir of the disk to planetesimals depends on the location of the water snowline. Cooler disks with a closer-in water snowline are more efficient at producing planetesimals than hotter disks where the water snowline is located further away from the star. Therefore, low-mass stars tend to form planetesimals more efficiently, but any correlation may be overshadowed by the spread in disk properties.

scholarly journals Protoplanetary disks of T Tauri binary systems in the Orion nebula cluster

2012 ◽  
Vol 540 ◽  
pp. A46 ◽  
Author(s):  
S. Daemgen ◽  
S. Correia ◽  
M. G. Petr-Gotzens
Keyword(s):  
Binary Systems ◽  
Protoplanetary Disks ◽  
Orion Nebula ◽  
T Tauri
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