The structure of protostellar accretion disks and the origin of bipolar flows

Wardle, Mark; Koenigl, Arieh

doi:10.1086/172739

Cited by 264 publications

(267 citation statements)

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“…The model has successfully been applied to low-mass T Tauri stars and explains the formation of jets A&A 562, A104 (2014) and their properties well (e.g., Königl 1991;Wardle & Königl 1993;Königl & Pudritz 2000;Ferreira et al 2006;Ferreira 2007 andLima et al 2010).…”

Section: Disk Wind Modelmentioning

confidence: 99%

Hydrogen lines as a diagnostic tool for studying multicomponent emitting regions in hot young stars: magnetosphere, X-wind, and disk wind

Тамбовцева

Гринин

Weigelt

2014

A&A

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Infrared interferometric observations with high spatial and spectral resolution and their quantitative modeling provide us with a unique opportunity to improve our understanding of the circumstellar environment of young stars and the accretion-ejection process. The goal of this paper is to investigate various models of the emitting regions in young Herbig Ae/Be stars that consist of (i) a compact rotating magnetosphere; (ii) an X-wind; and (iii) a disk wind. These models can be used, for example, to quantitatively interpret line profile measurements and infrared interferometric observations with the AMBER instrument of the Very Large Telescope Interferometer (VLTI) in the high spectral resolution mode (R = 12 000). VLTI/AMBER observations allow us to resolve the disk wind region and study the flux contribution of the unresolved magnetosphere and X-wind region to the total line flux. Analyzing the results of our non-LTE calculations, we conclude that the mechanisms of the different broadening of emission lines of different series include (1) the kinematic expansion due to the motion of the outflowing, accelerating gas in the magneto-centrifugal disk wind; (2) the Stark effect; and (3) the rotation of the magnetosphere. We also investigated extinction effects that can influence the shape of the line profiles. We considered the obscuration of the outer disk wind by an opaque dust and gas disk, the obscuration of the disk wind by a flared disk or by dust in the disk wind itself, and absorption of the star and disk continuum radiation in the disk wind along the line of sight. We show that due to extinction effects, the line profiles can change from double-peaked to single-peaked and P Cygni profiles. We studied the contribution of the different components of the stellar environment to different hydrogen emission lines and investigated how this contribution is dependent on the model parameters. The results of this study can be used for the detailed modeling of the emitting regions of individual young stars.

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Section: Disk Wind Modelmentioning

confidence: 99%

Hydrogen lines as a diagnostic tool for studying multicomponent emitting regions in hot young stars: magnetosphere, X-wind, and disk wind

Тамбовцева

Гринин

Weigelt

2014

A&A

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“…For example, field diffusion allows matter to be accreted while leaving the magnetic field behind. In disk-driven wind models magnetic diffusion allows some of the disk material to be loaded onto field lines and flung outwards from the disk surfaces (Wardle & Königl 1993) while the remainder is accreted. Diffusion is also associated with energy dissipation and sets the inner scale of magnetic structures.…”

Section: Magnetic Diffusionmentioning

confidence: 99%

“…Magnetic fields may efficiently transport angular momentum in protoplanetary disks either via MHD turbulence driven by the magnetorotational instability (Balbus & Hawley 1991;Hawley, Gammie & Balbus 1994), by accelerating a wind from the disk surfaces (Blandford & Payne 1982;Wardle & Königl 1993), or by looping above the disk surface and linking different radii. Advection and/or stirring by magnetically-driven turbulence affects disk chemistry (e.g.…”

Section: Introductionmentioning

confidence: 99%

Magnetic fields in protoplanetary disks

Wardle

2007

Astrophys Space Sci

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334

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Magnetic fields likely play a key role in the dynamics and evolution of protoplanetary disks. They have the potential to efficiently transport angular momentum by MHD turbulence or via the magnetocentrifugal acceleration of outflows from the disk surface. Magnetically-driven mixing has implications for disk chemistry and evolution of the grain population, and the effective viscous response of the disk determines whether planets migrate inwards or outwards. However, the weak ionisation of protoplanetary disks means that magnetic fields may not be able to effectively couple to the matter. I examine the magnetic diffusivity in a minimum solar nebula model and present calculations of the ionisation equilibrium and magnetic diffusivity as a function of height from the disk midplane at radii of 1 and 5 AU. Dust grains tend to suppress magnetic coupling by soaking up electrons and ions from the gas phase and reducing the conductivity of the gas by many orders of magnitude. However, once grains have grown to a few microns in size their effect starts to wane and magnetic fields can begin to couple to the gas even at the disk midplane. Because ions are generally decoupled from the magnetic field by neutral collisions while electrons are not, the Hall effect tends to dominate the diffusion of the magnetic field when it is able to partially couple to the gas, except at the disk surfaces where the low density of neutrals permits the ions to remain attached to the field lines.For a standard population of 0.1µm grains the active surface layers have a combined column Σ active ≈ 2 g cm −2 at 1 AU; by the time grains have aggregated to 3 µm, Σ active ≈ 80 g cm −2 . Ionisation in the active layers is dominated by stellar x-rays. In the absence of grains, x-rays maintain magnetic coupling to 10% of

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“…The final speed of this centrifugal outflow depends strongly on the disk vertical structure (see e.g. Wardle & Koenigl 1993) which is certainly unknown. However, for barionic outflows to reach mildly relativistic speeds, some inital boost would be neccesary, which would be produced by heating or mechanically, by flaring activity and/or by radiation pressure.…”

Section: Basic Scenariomentioning

confidence: 99%

A lepto-hadronic model for high-energy emission from FR I radiogalaxies

Reynoso

Medina

Romero

2011

A&A

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Context. The well known radiogalaxy Cen A has been recently detected as a source of very high energy (VHE) γ-rays by the HESS experiment just before Fermi/LAT detected it at high energies (HE). The detection, together with that of M 87, established radiogalaxies as VHE γ-ray emitters. Aims. The aim of this work is to present a lepto-hadronic model for the VHE emission from the relativistic jets in FR I radiogalaxies. Methods. We consider that protons and electrons are accelerated in a compact region near the base of the jet, and they cool emitting multi wavelength radiation as propagating along the jet. The proton and electron distributions are obtained through steady-state transport equation taking into account acceleration, radiative and non-radiative cooling processes, as well as particle transport by convection. Results. Considering the effects of photon absorption at different wavelengths, we calculate the radiation emitted by the primary protons and electrons, as well as the contribution of secondaries particles (e ± , πs and μs). The expected high-energy neutrino signal is also obtained and the possibility of detections with KM3NeT and IceCube is discussed. Conclusions. The spectral energy distribution obtained in our model with an appropriate set of parameters for an extended emission zone can account for much of the observed spectra for both AGNs.

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The structure of protostellar accretion disks and the origin of bipolar flows

Cited by 264 publications

References 0 publications

Hydrogen lines as a diagnostic tool for studying multicomponent emitting regions in hot young stars: magnetosphere, X-wind, and disk wind

Hydrogen lines as a diagnostic tool for studying multicomponent emitting regions in hot young stars: magnetosphere, X-wind, and disk wind

Magnetic fields in protoplanetary disks

A lepto-hadronic model for high-energy emission from FR I radiogalaxies

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