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

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.

scholarly journals The Flying Saucer: Tomography of the thermal and density gas structure of an edge-on protoplanetary disk

2017 ◽  
Vol 607 ◽  
pp. A130 ◽  
Author(s):  
A. Dutrey ◽  
S. Guilloteau ◽  
V. Piétu ◽  
E. Chapillon ◽  
V. Wakelam ◽  
...  
Keyword(s):  
Thermal Structure ◽  
Direct Determination ◽  
Molecular Data ◽  
Temperature Structure ◽  
Gas Temperature ◽  
Star Forming ◽  
Star Forming Regions ◽  
Flying Saucer ◽  
Grain Properties

Context. Determining the gas density and temperature structures of protoplanetary disks is a fundamental task in order to constrain planet formation theories. This is a challenging procedure and most determinations are based on model-dependent assumptions. Aims. We attempt a direct determination of the radial and vertical temperature structure of the Flying Saucer disk, thanks to its favorable inclination of 90 degrees. Methods. We present a method based on the tomographic study of an edge-on disk. Using ALMA, we observe at 0.5″ resolution the Flying Saucer in CO J = 2–1 and CS J = 5–4. This edge-on disk appears in silhouette against the CO J = 2–1 emission from background molecular clouds in ρ Oph. The combination of velocity gradients due to the Keplerian rotation of the disk and intensity variations in the CO background as a function of velocity provide a direct measure of the gas temperature as a function of radius and height above the disk mid-plane. Results. The overall thermal structure is consistent with model predictions, with a cold (<12−15 K) CO-depleted mid-plane and a warmer disk atmosphere. However, we find evidence for CO gas along the mid-plane beyond a radius of about 200 au, coincident with a change of grain properties. Such behavior is expected in the case of efficient rise of UV penetration re-heating the disk and thus allowing CO thermal desorption or favoring direct CO photo-desorption. CO is also detected at up to 3–4 scale heights, while CS is confined to around 1 scale height above the mid-plane. The limits of the method due to finite spatial and spectral resolutions are also discussed. Conclusions. This method appears to be a very promising way to determine the gas structure of planet-forming disks, provided that the molecular data have an angular resolution which is high enough, on the order of 0.3−0.1″ at the distance of the nearest star-forming regions.

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

2019 ◽  
Vol 885 (1) ◽  
pp. 91 ◽  
Author(s):  
Joanna Dra̧żkowska ◽  
Shengtai Li ◽  
Til Birnstiel ◽  
Sebastian M. Stammler ◽  
Hui Li
Keyword(s):  
Protoplanetary Disks ◽  
Hydrodynamic Models ◽  
Dust Evolution

scholarly journals Dust Evolution in Protoplanetary Disks

2018 ◽  
pp. 1-16
Author(s):  
Sean M. Andrews ◽  
Tilman Birnstiel
Keyword(s):  
Protoplanetary Disks ◽  
Dust Evolution

Retention of Small Charged Dust in Planet Forming Disks

2018 ◽  
Vol 14 (S345) ◽  
pp. 283-284
Author(s):  
Vitaly Akimkin
Keyword(s):  
Coulomb Repulsion ◽  
Central Star ◽  
Charged Dust ◽  
Micron Size ◽  
Disk Evolution ◽  
Small Grains ◽  
Fast Drift ◽  
Dust Grain ◽  
Dust Evolution ◽  
Dust Charging

AbstractDust evolution in disks around young stars is a key ingredient for the global disk evolution and accompanying planet formation. The mutual sticking of initially small grains is not straightforward and can be hampered by several processes. This includes dust grain bouncing, fragmentation, electrostatic repulsion and fast drift to the central star. In this study we aim at theoretical modeling of the dust coagulation coupled with the dust charging and disk ionization calculations. We show that the electrostatic barrier is a strong restraining factor to the coagulation of micron-size dust. While the sustained turbulence helps to overcome the electrostatic barrier, dust fluffiness limits this opportunity. Coulomb repulsion may keep a significant fraction of m dust in large regions of protoplanetary disks.

Magnetic Accretion Funnels in Young Stellar Objects: Thermal Structure and Emission Signatures

1997 ◽  
Vol 163 ◽  
pp. 760-760
Author(s):  
Steven C. Martin ◽  
Arieh Königl
Keyword(s):  
Magnetic Field ◽  
Near Infrared ◽  
Thermal Structure ◽  
Line Emission ◽  
Young Stellar Objects ◽  
Rate Equations ◽  
Gas Temperature ◽  
Ionization State ◽  
Object A ◽  
T Tauri

AbstractA self-consistent procedure is outlined for determining the thermal structure of gas inflowing along magnetic field lines of a young stellar object. A young pre-main-sequence star (e.g., a classical T Tauri star) is assumed to possess a dipole magnetic field that disrupts a geometrically thin accretion disk and channels the incoming gas toward the stellar surface, leading to the formation of a pair of accretion funnels that terminate in shocks at high stellar latitudes. The heat equation is solved together with the rate equations for hydrogen, and the main physical processes that heat and cool the gas are identified. In particular, in the case of T Tauri stars, it is found that adiabatic compression is the principal heat source and that the Ca II and Mg II ions act as a powerful thermostat that regulates the gas temperature. The ionization state of the gas in the radiation field of the stellar photosphere and of the accretion shocks is found in this case to be controlled by Balmer continuum photons. The implications of these calculations to the observational signatures of accreting YSOs (e.g., their near-infrared hydrogen and CO overtone line emission) are discussed.

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.

scholarly journals Disk Masses and Dust Evolution of Protoplanetary Disks around Brown Dwarfs

2021 ◽  
Vol 921 (2) ◽  
pp. 182
Author(s):  
Anneliese M. Rilinger ◽  
Catherine C. Espaillat
Keyword(s):  
Planet Formation ◽  
Spectral Energy ◽  
Star Forming ◽  
Star Forming Regions ◽  
Disk Mass ◽  
T Tauri ◽  
Multiple Regions ◽  
Disk Evolution ◽  
Dust Grain ◽  
Dust Evolution

Abstract We present the largest sample of brown dwarf (BD) protoplanetary disk spectral energy distributions modeled to date. We compile 49 objects with ALMA observations from four star-forming regions: ρ Ophiuchus, Taurus, Lupus, and Upper Scorpius. Studying multiple regions with various ages enables us to probe disk evolution over time. Specifically, from our models, we obtain values for dust grain sizes, dust settling, and disk mass; we compare how each of these parameters vary between the regions. We find that disk mass decreases with age. We also find evidence of disk evolution (i.e., grain growth and significant dust settling) in all four regions, indicating that planet formation and disk evolution may begin to occur at earlier stages. We generally find that these disks contain too little mass to form planetary companions, though we cannot rule out that planet formation may have already occurred. Finally, we examine the disk mass–host mass relationship and find that BD disks are largely consistent with previously determined relationships for disks around T Tauri stars.

scholarly journals SILLi 1.0: A 1D Numerical Tool Quantifying the Thermal Effects of Sill Intrusions

2017 ◽  
Author(s):  
Karthik Iyer ◽  
Henrik Svensen ◽  
Daniel W. Schmid
Keyword(s):  
Thermal Effects ◽  
Thermal Evolution ◽  
Thermal Structure ◽  
Sedimentary Basins ◽  
Gas Generation ◽  
Porosity Evolution ◽  
Karoo Basin ◽  
Igneous Intrusions ◽  
User Friendly ◽  
Latent Heats

Abstract. Igneous intrusions in sedimentary basins may have a profound effect on the thermal structure and physical properties of the hosting sedimentary rocks. These include mechanical effects such as deformation and uplift of sedimentary layers, generation of overpressure, mineral reactions and porosity evolution, and fracturing and vent formation following devolatilization reactions and the generation of CO2 and CH4. The gas generation and subsequent migration and venting may have contributed to several of the past climatic changes such as the end-Permian event and the Paleocene-Eocene Thermal Maximum. Additionally, the generation and expulsion of hydrocarbons and cracking of pre-existing oil reservoirs around a hot magmatic intrusion is of significant interest to the energy industry. In this paper, we present a user-friendly 1D FEM based tool, SILLi, which calculates the thermal effects of sill intrusions on the enclosing sedimentary stratigraphy. The model is accompanied by three case studies of sills emplaced in two different sedimentary basins, the Karoo Basin in South Africa and the Vøring Basin offshore Norway. Input data for the model is the present-day well log or sedimentary column with an Excel input file and includes rock parameters such as thermal conductivity, total organic carbon (TOC) content, porosity, and latent heats. The model accounts for sedimentation and burial based on a rate calculated by the sedimentary layer thickness and age. Erosion of the sedimentary column is also included to account for realistic basin evolution. Multiple sills can be emplaced within the system with varying ages. The emplacement of a sill occurs instantaneously. The model can be applied to volcanic sedimentary basins occurring globally. The model output includes the thermal evolution of the sedimentary column through time, and the changes that take place following sill emplacement such as TOC changes, thermal maturity, and the amount of organic and carbonate-derived CO2. The TOC and vitrinite results can be readily benchmarked within the tool to present-day values measured within the sedimentary column. This allows the user to determine the conditions required to obtain results that match observables and leads to a better understanding of metamorphic processes in sedimentary basins.

scholarly journals Gas vs dust radial extent in disks: the importance of their thermal interplay

2017 ◽  
Vol 13 (S332) ◽  
pp. 129-136
Author(s):  
Stefano Facchini
Keyword(s):  
Thermal Structure ◽  
Sharp Decrease ◽  
Outer Edge ◽  
Outer Radius ◽  
Gas Temperature ◽  
Secular Evolution ◽  
Radial Extent ◽  
Grain Size Distributions ◽  
The Difference ◽  
Dust Grain

AbstractA key parameter governing the secular evolution of protoplanetary disks is their outer radius. In this paper, the feedback of realistic dust grain size distributions onto the gas emission is investigated. Models predict that the difference of dust and gas extents as traced by CO is primarily caused by differences in the optical depth of lines vs continuum. The main effect of radial drift is the sharp decrease in the intensity profile at the outer edge. The gas radial extent can easily range within a factor of 2 for models with different turbulence. A combination of grain growth and vertical settling leads to thermal de-coupling between gas and dust at intermediate scale-heights. A proper treatment of the gas thermal structure within dust gaps will be fundamental to disentangle surface density gaps from gas temperature gaps.

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