scholarly journals The Effects of Metallicity and Grain Size on Gravitational Instabilities in Protoplanetary Disks

2005 ◽  
Vol 636 (2) ◽  
pp. L149-L152 ◽  
Author(s):  
Kai Cai ◽  
Richard H. Durisen ◽  
Scott Michael ◽  
Aaron C. Boley ◽  
Annie C. Mejía ◽  
...  
Keyword(s):  
Grain Size ◽  
Protoplanetary Disks ◽  
Gravitational Instabilities

scholarly journals Polarized emission by aligned grains in the Mie regime: Application to protoplanetary disks observed by ALMA

2020 ◽  
Vol 634 ◽  
pp. L15 ◽  
Author(s):  
V. Guillet ◽  
J. M. Girart ◽  
A. J. Maury ◽  
F. O. Alves
Keyword(s):  
Magnetic Field ◽  
Grain Size ◽  
Thermal Emission ◽  
Protoplanetary Disks ◽  
Polarization Vector ◽  
Size Distributions ◽  
Negative Polarization ◽  
Polarized Emission ◽  
Grain Size Distributions ◽  
The Magnetic Field

Context. The azimuthal polarization patterns observed in some protoplanetary disks by the Atacama Large Millimetre Array (ALMA) at millimeter wavelengths have raised doubts about whether they are truly produced by dust grains that are aligned with the magnetic field lines. These conclusions were based on the calculations of dust polarized emission in the Rayleigh regime, that is, for grain sizes that are much smaller than the wavelength. However, the grain size in such disks is typically estimated to be in the range of 0.1−1 mm from independent observations. Aims. We study the dust polarization properties of aligned grains in emission in the Mie regime, that is, when the mean grain size approaches the wavelength. Methods. By using the T-MATRIX and DustEM codes, we computed the spectral dependence of the polarization fraction in emission for grains in perfect spinning alignment for various grain size distributions. We restricted our study to weakly-elongated oblate and prolate grains of astrosilicate composition that have a mean size ranging from 10 μm to 1 mm. Results. In the submillimeter and millimeter wavelength range, the polarization by B-field aligned grains becomes negative for grains larger than ∼250 μm, meaning that the polarization vector becomes parallel to the B-field. The transition from the positive to the negative polarization occurs at a wavelength of λ ∼ 1 mm. The regime of negative polarization does not exist for grains that are smaller than ∼100 μm. Conclusions. When using realistic grain size distributions for disks with grains up to the submillimeter sizes, the polarization direction of thermal emission by aligned grains is shown to be parallel to the direction of the magnetic field over a significant fraction of the wavelengths typically used to observe young protoplanetary disks. This property may explain the peculiar azimuthal orientation of the polarization vectors in some of the disks observed with ALMA and attest to the conserved ability of dust polarized emission to trace the magnetic field in disks.

The Thermal Regulation of Gravitational Instabilities in Protoplanetary Disks

2003 ◽  
Vol 590 (2) ◽  
pp. 1060-1080 ◽  
Author(s):  
Brian K. Pickett ◽  
Annie C. Mejia ◽  
Richard H. Durisen ◽  
Patrick M. Cassen ◽  
Donald K. Berry ◽  
...  
Keyword(s):  
Protoplanetary Disks ◽  
Thermal Regulation ◽  
Gravitational Instabilities

scholarly journals The Thermal Regulation of Gravitational Instabilities in Protoplanetary Disks. IV. Simulations with Envelope Irradiation

2008 ◽  
Vol 673 (2) ◽  
pp. 1138-1153 ◽  
Author(s):  
Kai Cai ◽  
Richard H. Durisen ◽  
Aaron C. Boley ◽  
Megan K. Pickett ◽  
Annie C. Mejia
Keyword(s):  
Protoplanetary Disks ◽  
Thermal Regulation ◽  
Gravitational Instabilities

scholarly journals Probing protoplanetary disks with Aperture Masking

2013 ◽  
Vol 8 (S299) ◽  
pp. 119-120
Author(s):  
S. Lacour ◽  
P. Tuthill ◽  
S. Casassus
Keyword(s):  
Dynamic Range ◽  
Protoplanetary Disks ◽  
Theoretical Models ◽  
Diffraction Limit ◽  
Long Baseline ◽  
Gravitational Instabilities ◽  
Core Accretion ◽  
Differential Imaging ◽  
Unique Ability ◽  
Orbital Migration

AbstractThe interaction between planetary formation and protostellar disks is among the most critical remaining pieces in the puzzle of solar system assembly. Leading theoretical models are constructed around two distinct scenarios: gravitational instabilities and core accretion. The physics of each applies to quite different epochs of formation, and exhibits complex dependencies on parameters like disk density and viscosity. Untangling the effects such processes have on the final planetary statistics necessitates direct observation of exoplanets in their primordial state, prior to orbital migration. Furthermore, detailed study of the environment, such as the way the planets shape the protostellar disk by driving accretion streams across disk gaps, will also constrain formation models. Aperture masking interferometry has demonstrated a unique ability to probe the gaps within stellar disks. It has twin advantages of a higher dynamic range at the diffraction limit (λ/D) than differential imaging, while at the same time giving very extensive UV coverage compared to long baseline interferometry.

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