Sub-Keplerian accretion onto circumstellar disks

Visser, R.; Dullemond, C. P.

doi:10.1051/0004-6361/200913604

Cited by 35 publications

(49 citation statements)

References 82 publications

(127 reference statements)

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“…Our revised solution to the problem of sub-Keplerian accretion (Visser & Dullemond 2010) results in radial velocity profiles that are different from the ones in Paper I. With the old profiles, all material that accretes inside of the snow line always remains inside of the snow line.…”

Section: Comets: Mixed Origins?mentioning

confidence: 81%

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The chemical history of molecules in circumstellar disks

Visser

Doty

Dishoeck

2011

A&A

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Context. The chemical composition of a molecular cloud changes dramatically as it collapses to form a low-mass protostar and circumstellar disk. Two-dimensional (2D) chemodynamical models are required to properly study this process. Aims. The goal of this work is to follow, for the first time, the chemical evolution in two dimensions all the way from a pre-stellar core into a circumstellar disk. Of special interest is the question whether the chemical composition of the disk is a result of chemical processing during the collapse phase, or whether it is determined by in situ processing after the disk has formed. Methods. Our model combines a semi-analytical method to get 2D axisymmetric density and velocity structures with detailed radiative transfer calculations to get temperature profiles and UV fluxes. Material is followed in from the core to the disk and a full gas-phase chemistry network -including freeze-out onto and evaporation from cold dust grains -is evolved along these trajectories. The abundances thus obtained are compared to the results from a static disk model and to observations of comets. Results. The chemistry during the collapse phase is dominated by a few key processes, such as the evaporation of CO or the photodissociation of H 2 O. Depending on the physical conditions encountered along specific trajectories, some of these processes are absent. At the end of the collapse phase, the disk can be divided into zones with different chemical histories. The disk is not in chemical equilibrium at the end of the collapse, so care must be taken when choosing the initial abundances for stand-alone disk chemistry models. Our model results imply that comets must be formed from material with different chemical histories: some of it is strongly processed, some of it remains pristine. Variations between individual comets are possible if they formed at different positions or different times in the solar nebula.

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Section: Comets: Mixed Origins?mentioning

confidence: 81%

“…The model, described in detail by Visser et al (2009b) and Visser & Dullemond (2010), consists of semi-analytical density and velocity profiles throughout the core and the disk. The dust temperature and the UV radiation field -both important for the chemical evolution -are calculated with a full radiative transfer method.…”

Section: Discussionmentioning

confidence: 99%

The chemical history of molecules in circumstellar disks

Visser

Doty

Dishoeck

2011

A&A

Self Cite

141

193

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“…We briefly present features of the model; more details can be found in the original papers. The model describes the temporal evolution of the density and velocity fields in a semianalytical manner, following the inside-out collapse model with the effect of rotation (Shu, 1977;Cassen & Moosman, 1981;Terebey et al, 1984) and the one-dimensional accretion disk model with the α viscosity prescription (Shakura & Sunyaev, 1973;Lynden-Bell et al, 1974;Visser & Dullemond, 2010). The vertical density structure of the disk is set by the assump- Fig.…”

Section: Physical Modelmentioning

confidence: 99%

Water delivery from cores to disks: Deuteration as a probe of the prestellar inheritance of H₂O

Furuya

Drozdovskaya

Visser

et al. 2017

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We investigate the delivery of regular and deuterated forms of water from prestellar cores to circumstellar disks. We adopt a semianalytical axisymmetric two-dimensional collapsing core model with post-processing gas-ice astrochemical simulations, in which a layered ice structure is considered. The physical and chemical evolutions are followed until the end of the main accretion phase. When mass averaged over the whole disk, a forming disk has a similar H 2 O abundance and HDO/H 2 O abundance ratio as their precollapse values (within a factor of 2), regardless of time in our models. Consistent with previous studies, our models suggest that interstellar water ice is delivered to forming disks without significant alteration. On the other hand, the local vertically averaged H 2 O ice abundance and HDO/H 2 O ice ratio can differ more, by up to a factor of several, depending on time and distance from a central star. Key parameters for the local variations are the fluence of stellar UV photons en route into the disk and the ice layered structure, the latter of which is mostly established in the prestellar stages. We also find that even if interstellar water ice is destroyed by stellar UV and (partly) reformed prior to disk entry, the HDO/H 2 O ratio in reformed water ice is similar to the original value. This finding indicates that some caution is needed in discussions on the prestellar inheritance of H 2 O based on comparisons between the observationally derived HDO/H 2 O ratio in clouds/cores and that in disks/comets. Alternatively, we propose that the ratio of D 2 O/HDO to HDO/H 2 O better probes the prestellar inheritance of H 2 O. It is also found that icy organics are more enriched in deuterium than water ice in forming disks. The differential deuterium fractionation in water and organics is inherited from the prestellar stages.

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“…For comparison, synthetic images from 2D semi-analytical axisymmetric models of collapsing rotating envelope and disk formation as described in Visser et al (2009) with modifications introduced in Visser & Dullemond (2010) and Harsono et al (2013) are also simulated. These models are based on the collapse and disk formation solutions of Terebey et al (1984) and Cassen & Moosman (1981) including a prescription for an outflow cavity.…”

Section: Semi-analytical Modelmentioning

confidence: 99%

“…The disk evolution follows the α-disk formalism as described in Shakura & Sunyaev (1973) and Lynden-Bell & Pringle (1974). The disk surface is defined by hydrostatic equilibrium as described in Visser & Dullemond (2010) is assumed to be in Keplerian rotation. To compare with the MHD simulations, we consider the collapse of the 1 M , c s = 0.26 km s −1 , and Ω 0 = 10 −13 Hz core.…”

Section: Semi-analytical Modelmentioning

confidence: 99%

Testing protostellar disk formation models with ALMA observations

Harsono

Dishoeck

Bruderer

et al. 2015

A&A

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Context. Recent simulations have explored different ways to form accretion disks around low-mass stars. However, it has been difficult to differentiate between the proposed mechanisms because of a lack of observable predictions from these numerical studies. Aims. We aim to present observables that can differentiate a rotationally supported disk from an infalling rotating envelope toward deeply embedded young stellar objects (M env > M disk ) and infer their masses and sizes. Methods. Two 3D magnetohydrodynamics (MHD) formation simulations are studied with a rotationally supported disk (RSD) forming in one but not the other (where a pseudo-disk is formed instead), together with the 2D semi-analytical model. We determine the dust temperature structure through continuum radiative transfer RADMC3D modeling. A simple temperature-dependent CO abundance structure is adopted and synthetic spectrally resolved submm rotational molecular lines up to J u = 10 are compared with existing data to provide predictions for future ALMA observations. Results. The 3D MHD simulations and 2D semi-analytical model predict similar compact components in continuum if observed at the spatial resolutions of 0.5-1 (70-140 AU) typical of the observations to date. A spatial resolution of ∼14 AU and high dynamic range (>1000) are required in order to differentiate between RSD and pseudo-disk formation scenarios in the continuum. The first moment maps of the molecular lines show a blue-to red-shifted velocity gradient along the major axis of the flattened structure in the case of RSD formation, as expected, whereas it is along the minor axis in the case of a pseudo-disk. The peak position-velocity diagrams indicate that the pseudo-disk shows a flatter velocity profile with radius than does an RSD. On larger scales, the CO isotopolog line profiles within large (>9 ) beams are similar and are narrower than the observed line widths of low-J (2-1 and 3-2) lines, indicating significant turbulence in the large-scale envelopes. However a forming RSD can provide the observed line widths of high-J (6-5, 9-8, and 10-9) lines. Thus, either RSDs are common or a higher level of turbulence (b ∼ 0.8 km s −1 ) is required in the inner envelope compared with the outer part (0.4 km s −1 ). Conclusions. Multiple spatially and spectrally resolved molecular line observations can differentiate between the pseudo-disk and the RSD much better than continuum data. The continuum data give a better estimate of disk masses, whereas the disk sizes can be estimated from the spatially resolved molecular lines observations. The general observable trends are similar between the 2D semi-analytical models and 3D MHD RSD simulations.

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Sub-Keplerian accretion onto circumstellar disks

Cited by 35 publications

References 82 publications

The chemical history of molecules in circumstellar disks

The chemical history of molecules in circumstellar disks

Water delivery from cores to disks: Deuteration as a probe of the prestellar inheritance of H₂O

Testing protostellar disk formation models with ALMA observations

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Sub-Keplerian accretion onto circumstellar disks

Cited by 35 publications

References 82 publications

The chemical history of molecules in circumstellar disks

The chemical history of molecules in circumstellar disks

Water delivery from cores to disks: Deuteration as a probe of the prestellar inheritance of H2O

Testing protostellar disk formation models with ALMA observations

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Water delivery from cores to disks: Deuteration as a probe of the prestellar inheritance of H₂O