Investigation of the Physical Properties of Protoplanetary Disks around T Tauri Stars by a 1 Arcsecond Imaging Survey: Evolution and Diversity of the Disks in Their Accretion Stage

Kitamura, Yoshihisa; Momose, Munetake; Yokogawa, Shinji; Kawabe, Ryohei; Tamura, Motohide; Ida, Shigeru

doi:10.1086/344223

Cited by 192 publications

(262 citation statements)

References 89 publications

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“…While this is broadly consistent with observed protoplanetary disks (Kitamura et al 2002), it is possible to have surface densities 30-50 times higher without suffering gravitational instability. The approximate effect of adding material to the disk is to multiply up the density everywhere by the same factor.…”

Section: Discussionsupporting

confidence: 89%

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Magnetic fields in protoplanetary disks

Wardle

2007

Astrophys Space Sci

255

341

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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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Section: Discussionsupporting

confidence: 89%

“…Kitamura et al 2002;Andrews & Williams 2005). The isothermal sound speed in the disk implied by this temperature profile is…”

Section: Minimum-mass Solar Nebulamentioning

confidence: 93%

Magnetic fields in protoplanetary disks

Wardle

2007

Astrophys Space Sci

255

341

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“…4) require larger disk radii to reproduce the observed images, the best match in this case is for R ∼ 300 AU. Shallow surface density gradients have been recently claimed for many TTS disks (Kitamura et al 2002); the comparison of our CQ Tau map with models with p = 0.5 is shown in Fig. 5.…”

Section: Modelsmentioning

confidence: 69%

Large grains in the disk of CQ Tau

Testi

Natta

Shepherd

et al. 2003

A&A

196

193

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Abstract. We present 7 mm observations of the dusty disk surrounding the 10 Myr old 1.5 M pre-main-sequence star CQ Tauri obtained at the Very Large Array with 0.8 arcsec resolution and 0.1 mJy rms sensitivity. These observations resolve the 7 mm emission in approximately the north-south direction, confirming previous results obtained with lower resolution. We use a twolayer flared disk model to interpret the observed fluxes from 7 mm to 1.3 mm together with the resolved 7 mm structure. We find that the disk radius is constrained to the range 100 to 300 AU, depending on the steepness of the disk surface density distribution. The power law index of the dust opacity coefficient, β, is constrained to be 0.5 to 0.7. Since the models indicate that the disk is optically thin at millimeter wavelengths for radii greater than 8 AU, the contribution of an optically thick region to the emission is less than 10%. This implies that high optical depth or complex disk geometry cannot be the cause of the observed shallow millimeter spectral index. Instead, the new analysis supports the earlier suggestion that dust particles in the disk have grown to sizes as large as a few centimeters. The dust in the CQ Tauri system appears to be evolved much like that in the TW Hydra system, a well-studied pre-main-sequence star of similar age and lower mass. The survival of gas-rich disks with incomplete grain evolution at such old ages deserves further investigations.

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“…For a solar-mass star, this typically requires a disk with a mass of ∼0.1 M . Estimated disk masses for T Tauri stars with ages of a few Myr range from 0.01 to 0.1 M (Kitamura et al 2002), suggesting that at least some protoplanetary disks are massive enough to form gas giant planets by disk instability. Current estimates are that roughly 10% of nearby solar-type stars harbor gas giant planets with masses greater than that of Saturn inside 3 AU (Cumming et al 2008).…”

Section: Disk Instabilitymentioning

confidence: 99%

Metallicity and Planet Formation: Models

Boss

2009

Proc. IAU

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Abstract. Planets typically are considerably more metal-rich than even the most metal-rich stars, one indication that planet formation must differ greatly from star formation. There is general agreement that terrestrial planets form by the collisional accumulation of solids composed of heavy elements in the inner regions of protoplanetary disks. Two competing mechanisms exist for the formation of giant planets, core accretion and disk instability, though hybrid combinations are possible as well. In core accretion, a higher metallicity in the protoplanetary disk leads directly to larger core masses and hence to more gas giant planets. Given the strong correlation of gas giant planets detected by Doppler spectroscopy with stellar metallicity, this has often been taken as proof that core accretion is the mechanism that forms giant planets. Recent work, however, implies that the formation of gas giants by disk instability can be enhanced by higher metallicities, though not as dramatically as for core accretion. In both scenarios, the ongoing accretion of planetesimals by gas giant protoplanets leads to strong enrichments of heavy elements in their gaseous envelopes. Both scenarios also imply that gas giant planets should have significant solid cores, raising questions for gas giant interior models without cores. Exoplanets with large inferred core masses seem likely to have formed by core accretion, while gas giants at distances beyond 20 AU seem more likely to have formed by disk instability. Given the wide variety of exoplanets found to date, it appears that both mechanisms are needed to explain the formation of the known population of giant planets.

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Investigation of the Physical Properties of Protoplanetary Disks around T Tauri Stars by a 1 Arcsecond Imaging Survey: Evolution and Diversity of the Disks in Their Accretion Stage

Cited by 192 publications

References 89 publications

Magnetic fields in protoplanetary disks

Magnetic fields in protoplanetary disks

Large grains in the disk of CQ Tau

Metallicity and Planet Formation: Models

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