scholarly journals The origin of tail-like structures around protoplanetary disks

2020 ◽  
Vol 635 ◽  
pp. A196
Author(s):  
Eduard I. Vorobyov ◽  
Alexandr M. Skliarevskii ◽  
Vardan G. Elbakyan ◽  
Michihiro Takami ◽  
Hauyu Baobab Liu ◽  
...  
Keyword(s):  
Protoplanetary Disks ◽  
Bow Shock ◽  
Brown Dwarf ◽  
Unique Type ◽  
Close Encounters ◽  
Protostellar Disks ◽  
Numerical Hydrodynamics ◽  
Dust Dynamics ◽  
Fu Ori ◽  
Dust Flow

Aims. We study the origin of tail-like structures recently detected around the disk of SU Aurigae and several FU Orionis-type stars. Methods. Dynamic protostellar disks featuring ejections of gaseous clumps and quiescent protoplanetary disks experiencing a close encounter with an intruder star were modeled using the numerical hydrodynamics code FEOSAD. Both the gas and dust dynamics were taken into account, including dust growth and mutual friction between the gas and dust components. Only plane-of-the-disk encounters were considered. Results. Ejected clumps produce a unique type of tail that is characterized by a bow-shock shape. Such tails originate from the supersonic motion of ejected clumps through the dense envelope that often surrounds young gravitationally unstable protostellar disks. The ejected clumps either sit at the head of the tail-like structure or disperse if their mass is insufficient to withstand the head wind of the envelope. On the other hand, close encounters with quiescent protoplanetary disks produce three types of the tail-like structure; we define these as pre-collisional, post-collisional, and spiral tails. These tails can in principle be distinguished from one another by particular features of the gas and dust flow in and around them. We find that the brown-dwarf-mass intruders do not capture circumintruder disks during the encounter, while the subsolar-mass intruders can acquire appreciable circumintruder disks with elevated dust-to-gas ratios, which can ease their observational detection. However, this is true only for prograde collisions; the retrograde intruders fail to collect appreciable amounts of gas or dust from the disk of the target. The mass of gas in the tail varies in the range 0.85–11.8 MJup, while the total mass of dust lies in the 1.75–30.1 M⊕ range, with the spiral tails featuring the highest masses. The predicted mass of dust in the model tail-like structures is therefore higher than what was inferred for similar structures in SU Aur, FU Ori, and Z CMa, making their observational detection feasible. Conclusions. Tail-like structures around protostellar and protoplanetary disks can be used to infer interesting phenomena such as clump ejection or close encounters. In particular, the bow-shock morphology of the tails could point to clump ejections as a possible formation mechanism. Further numerical and observational studies are needed to better understand the detectability and properties of the tails.

scholarly journals Chemical modeling of FU Ori protoplanetary disks

2018 ◽  
Vol 14 (S345) ◽  
pp. 367-368
Author(s):  
Tamara Molyarova ◽  
Vitaly Akimkin ◽  
Dmitry Semenov ◽  
Péter Ábrahám ◽  
Thomas Henning ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Protoplanetary Disks ◽  
Protoplanetary Disk ◽  
Chemical Processes ◽  
Molecular Composition ◽  
Chemical Modeling ◽  
Fu Ori

AbstractLuminosity outbursts of the FU Ori type stars, which have a magnitude of ∼ 100 L⊙ and last for decades, may affect chemical composition of the surrounding protoplanetary disk. Using astrochemical modelling we analyse the changes induced by the outburst and search for species sensitive to the luminosity rise. Some changes in the disk molecular composition appear not only during the outburst itself but can also retain for decades after the end of the outburst. We analyse main chemical processes responsible for these effects and assess timescales at which chemically inert species return to the pre-outburst abundances.

scholarly journals Characterizing young protostellar disks with the CALYPSO IRAM-PdBI survey: large Class 0 disks are rare

2019 ◽  
Vol 621 ◽  
pp. A76 ◽  
Author(s):  
A. J. Maury ◽  
Ph. André ◽  
L. Testi ◽  
S. Maret ◽  
A. Belloche ◽  
...  
Keyword(s):  
Size Distribution ◽  
Protoplanetary Disks ◽  
Continuum Emission ◽  
Formation Mechanisms ◽  
Multiple Systems ◽  
Protostellar Disks ◽  
Disk Size ◽  
Small Scales ◽  
Prestellar Cores ◽  
Protostellar Collapse

Context. Understanding the formation mechanisms of protoplanetary disks and multiple systems and also their pristine properties are key questions for modern astrophysics. The properties of the youngest disks, embedded in rotating infalling protostellar envelopes, have largely remained unconstrained up to now. Aims. We aim to observe the youngest protostars with a spatial resolution that is high enough to resolve and characterize the progenitors of protoplanetary disks. This can only be achieved using submillimeter and millimeter interferometric facilities. In the framework of the IRAM Plateau de Bure Interferometer survey CALYPSO, we have obtained subarcsecond observations of the dust continuum emission at 231 and 94 GHz for a sample of 16 solar-type Class 0 protostars. Methods. In an attempt to identify disk-like structures embedded at small scales in the protostellar envelopes, we modeled the dust continuum emission visibility profiles using Plummer-like envelope models and envelope models that include additional Gaussian disk-like components. Results. Our analysis shows that in the CALYPSO sample, 11 of the 16 Class 0 protostars are better reproduced by models including a disk-like dust continuum component contributing to the flux at small scales, but less than 25% of these candidate protostellar disks are resolved at radii >60 au. Including all available literature constraints on Class 0 disks at subarcsecond scales, we show that our results are representative: most (>72% in a sample of 26 protostars) Class 0 protostellar disks are small and emerge only at radii <60 au. We find a multiplicity fraction of the CALYPSO protostars ≲57% ± 10% at the scales 100–5000 au, which generally agrees with the multiplicity properties of Class I protostars at similar scales. Conclusions. We compare our observational constraints on the disk size distribution in Class 0 protostars to the typical disk properties from protostellar formation models. If Class 0 protostars contain similar rotational energy as is currently estimated for prestellar cores, then hydrodynamical models of protostellar collapse systematically predict a high occurrence of large disks. Our observations suggest that these are rarely observed, however. Because they reduce the centrifugal radius and produce a disk size distribution that peaks at radii <100 au during the main accretion phase, magnetized models of rotating protostellar collapse are favored by our observations.

scholarly journals Special Session 7 Young Stars, Brown Dwarfs, and Protoplanetary Disks

2009 ◽  
Vol 5 (H15) ◽  
pp. 727-728
Author(s):  
Jane Gregorio-Hetem ◽  
Silvia Alencar
Keyword(s):  
Adaptive Optics ◽  
Planet Formation ◽  
Protoplanetary Disks ◽  
Brown Dwarfs ◽  
Young Stars ◽  
Special Session ◽  
Brown Dwarf ◽  
X Ray ◽  
Substellar Objects

In recent years our knowledge of star, brown dwarf and planet formation has progressed immensely due to new data in the IR domain (Spitzer telescope), new X-ray campaigns such as the Chandra Orion Ultradeep Project (COUP) and the X-ray Emission Survey of Taurus (XEST), with XMM-Newton, as well as adaptive optics results and synoptic studies of young stellar and substellar objects.

scholarly journals Thermal evolution of protoplanetary disks: from β-cooling to decoupled gas and dust temperatures

2020 ◽  
Vol 638 ◽  
pp. A102 ◽  
Author(s):  
Eduard I. Vorobyov ◽  
Ryoki Matsukoba ◽  
Kazuyuki Omukai ◽  
Manuel Guedel
Keyword(s):  
Thermal Evolution ◽  
Thermal Structure ◽  
Protoplanetary Disks ◽  
Gas Temperature ◽  
Numerical Hydrodynamics ◽  
Variable Nature ◽  
Dynamical Time ◽  
Envelope Material ◽  
Disk Evolution ◽  
Dust Evolution

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.

scholarly journals Inner dusty regions of protoplanetary discs – II. Dust dynamics driven by radiation pressure and disc winds

2020 ◽  
Vol 500 (1) ◽  
pp. 506-519
Author(s):  
Dejan Vinković ◽  
Miljenko Čemeljić
Keyword(s):  
Radiation Pressure ◽  
Stationary Solutions ◽  
Density Distributions ◽  
Dust Dynamics ◽  
Dust Distribution ◽  
Porous Grains ◽  
Gas Drag ◽  
Dust Flow ◽  
Radiation Pressure Force ◽  
Protoplanetary Discs

ABSTRACT We explore dust flow in the hottest parts of protoplanetary discs using the forces of gravity, gas drag, and radiation pressure. Our main focus is on the optically thin regions of dusty disc, where the dust is exposed to the most extreme heating conditions and dynamical perturbations: the surface of optically thick disc and the inner dust sublimation zone. We utilize results from two numerically strenuous fields of research. The first is the quasi-stationary solutions on gas velocity and density distributions from mangetohydrodynamical (MHD) simulations of accretion discs. This is critical for implementing a more realistic gas drag impact on dust movements. The second is the optical depth structure from a high-resolution dust radiation transfer. This step is critical for a better understanding of dust distribution within the disc. We describe a numerical method that incorporates these solutions into the dust dynamics equations. We use this to integrate dust trajectories under different disc wind models and show how grains end up trapped in flows that range from simple accretion on to the star to outflows into outer disc regions. We demonstrate how the radiation pressure force plays one of the key roles in this process and cannot be ignored. It erodes the dusty disc surface, reduces its height, resists dust accretion on to the star, and helps the disc wind in pushing grains outwards. The changes in grain size and porosity significantly affect the results, with smaller and porous grains being influenced more strongly by the disc wind and radiation pressure.

scholarly journals The Onset of Planet Formation in Brown Dwarf Disks

Science ◽  
2005 ◽  
Vol 310 (5749) ◽  
pp. 834-836 ◽  
Author(s):  
Dániel Apai ◽  
Ilaria Pascucci ◽  
Jeroen Bouwman ◽  
Antonella Natta ◽  
Thomas Henning ◽  
...  
Keyword(s):  
Infrared Spectra ◽  
Planet Formation ◽  
Protoplanetary Disks ◽  
Brown Dwarfs ◽  
Circumstellar Disks ◽  
Dust Grains ◽  
Brown Dwarf ◽  
Intermediate Mass ◽  
Intermediate Mass Stars ◽  
Robust Process

The onset of planet formation in protoplanetary disks is marked by the growth and crystallization of sub–micrometer-sized dust grains accompanied by dust settling toward the disk mid-plane. Here, we present infrared spectra of disks around brown dwarfs and brown dwarf candidates. We show that all three processes occur in such cool disks in a way similar or identical to that in disks around low- and intermediate-mass stars. These results indicate that the onset of planet formation extends to disks around brown dwarfs, suggesting that planet formation is a robust process occurring in most young circumstellar disks.

Dust Dynamics in Protoplanetary Disks: Parallel Computing with PVM

2002 ◽  
Vol 176 (2) ◽  
pp. 276-294 ◽  
Author(s):  
Carlos de la Fuente Marcos ◽  
Pierre Barge ◽  
Raúl de la Fuente Marcos
Keyword(s):  
Parallel Computing ◽  
Protoplanetary Disks ◽  
Dust Dynamics

scholarly journals On the Possibility to Identify a Companion in a Protoplanetary Disk

2015 ◽  
Vol 10 (S314) ◽  
pp. 211-212
Author(s):  
O. V. Zakhozhay
Keyword(s):  
Energy Distribution ◽  
Profile Analysis ◽  
Spectral Energy Distribution ◽  
Protoplanetary Disks ◽  
Protoplanetary Disk ◽  
Spectral Energy ◽  
The Sun ◽  
Maximum Difference ◽  
Brown Dwarf ◽  
Energy Distributions

AbstractIn this paper, I investigate a possibility to detect a brown dwarf companion in a protoplanetary disk based on spectral energy distribution (SED) profile analysis. I present synthetic spectral energy distributions of protoplanetary disks with and without an embedded companion that clears a gap. The computations are performed for a star (0.8 M⊙) and a substellar companion (30 MJ) at an age of 5 Myr embedded in a protoplanetary disk, located at a distance 100 pc from the Sun. Analysis of the SED profile shape indicates that the maximum difference between the fluxes of the systems with and without the companion is ≈ 0.43 Jy at 34 μm.

scholarly journals Accretion bursts in low-metallicity protostellar disks

2020 ◽  
Vol 641 ◽  
pp. A72
Author(s):  
Eduard I. Vorobyov ◽  
Vardan G. Elbakyan ◽  
Kazuyuki Omukai ◽  
Takashi Hosokawa ◽  
Ryoki Matsukoba ◽  
...  
Keyword(s):  
Initial Conditions ◽  
Gravitational Instability ◽  
Mass Loading ◽  
Protostellar Disks ◽  
Numerical Hydrodynamics ◽  
Accretion Rates ◽  
Solar Metallicity ◽  
Disk Evolution ◽  
Low Metallicity ◽  
Cloud Cores

Aims. The early evolution of protostellar disks with metallicities in the Z = 1.0 − 0.01 Z⊙ range was studied with a particular emphasis on the strength of gravitational instability and the nature of protostellar accretion in low-metallicity systems. Methods. Numerical hydrodynamics simulations in the thin-disk limit were employed that feature separate gas and dust temperatures, and disk mass-loading from the infalling parent cloud cores. Models with cloud cores of similar initial mass and rotation pattern but distinct metallicity were considered to distinguish the effect of metallicity from that of the initial conditions. Results. The early stages of disk evolution in low-metallicity models are characterized by vigorous gravitational instability and fragmentation. Disk instability is sustained by continual mass-loading from the collapsing core. The time period that is covered by this unstable stage is much shorter in the Z = 0.01 Z⊙ models than in their higher metallicity counterparts thanks to the higher rates of mass infall caused by higher gas temperatures (which decouple from lower dust temperatures) in the inner parts of collapsing cores. Protostellar accretion rates are highly variable in the low-metallicity models reflecting the highly dynamic nature of the corresponding protostellar disks. The low-metallicity systems feature short but energetic episodes of mass accretion caused by infall of inward-migrating gaseous clumps that form via gravitational fragmentation of protostellar disks. These bursts seem to be more numerous and last longer in the Z = 0.1 Z⊙ models than in the Z = 0.01 Z⊙ case. Conclusions. Variable protostellar accretion with episodic bursts is not a particular feature of solar metallicity disks. It is also inherent to gravitationally unstable disks with metallicities up to 100 times lower than solar.

scholarly journals Embedded disks around low-mass protostars

2010 ◽  
Vol 6 (S270) ◽  
pp. 219-222
Author(s):  
Eduard I. Vorobyov ◽  
Shantanu Basu
Keyword(s):  
Core Mass ◽  
Multiple Systems ◽  
Protostellar Disks ◽  
Numerical Hydrodynamics ◽  
Accretion Rates ◽  
Low Mass ◽  
Sizeable Fraction ◽  
Phase Systems ◽  
Cloud Cores ◽  
Embedded Disks

AbstractThe time evolution of protostellar disks in the embedded phase of star formation (EPSF) is reviewed based on numerical hydrodynamics simulations of the gravitational collapse of two cloud cores with distinct initial masses. Special emphasis is given to disk, stellar, and envelope masses and also mass accretion rates onto the star. It is shown that accretion is highly variable in the EPSF, in agreement with recent theoretical and observational expectations. Protostellar disks quickly accumulate mass upon formation and may reach a sizeable fraction of the envelope mass (~35%) by the end of the Class 0 phase. Systems with disk-to-star mass ratio ξ≈0.5 are common but systems with ξ≥1.0 are rare because the latter quickly evolve into binary or multiple systems. Embedded disks are characterized by radial pulsations, the amplitude of which increases with growing core mass.

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