Surface Layer Accretion in Transitional and Conventional Disks: From Polycyclic Aromatic Hydrocarbons to Planets

Perez-Becker, Daniel; Chiang, Eugene

doi:10.1088/0004-637x/727/1/2

Cited by 93 publications

(54 citation statements)

References 98 publications

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“…Dead zone models that include more physics generally find active layer surface densities that may be very small (e.g., Bai 2011). However, such small active layers cannot explain accretion rates observed in T Tauri stars (e.g., Perez-Becker & Chiang 2011;Martin et al 2012b). Thus we fold all of the uncertainty into the parameter Σ crit .…”

Section: Caveatsmentioning

confidence: 99%

Nebular dead zone effects on the D/H ratio in chondrites and comets

Ali-Dib

Martin

Petit

et al. 2015

A&A

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Context. Comets and chondrites show non-monotonic behavior of their deuterium-to-hydrogen (D/H) ratio as a function of their formation location from the Sun. This is difficult to explain with a classical protoplanetary disk model that has a decreasing temperature structure with radius from the Sun. Aims. We want to understand if a protoplanetary disc with a dead zone, i.e., a region of zero or low turbulence, can explain the measured D/H values in comets and chondrites. Methods. We use time snapshots of a vertically layered disk model with turbulent surface layers and a dead zone at the midplane. The disc has a non-monotonic temperature structure due to increased heating from self-gravity in the outer parts of the dead zone. We couple this to a D/H ratio evolution model in order to quantify the effect of such thermal profiles on D/H enrichment in the nebula. Results. We find that the local temperature peak in the disk can explain the diversity in the D/H ratios of different chondritic families. This disk temperature profile leads to a non-monotonic D/H enrichment evolution, allowing these families to acquire their different D/H values while forming in close proximity. The formation order we infer for these families is compatible with that inferred from their water abundances. However, we find that even for very young disks, the thermal profile reversal is too close to the Sun to be relevant for comets.

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Section: Caveatsmentioning

confidence: 99%

Nebular dead zone effects on the D/H ratio in chondrites and comets

Ali-Dib

Martin

Petit

et al. 2015

A&A

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“…However, recent works suggest that ambipolar diffusion and the Hall effect may determine the active layer (e.g. Bai & Stone 2011; Perez‐Becker & Chiang 2011a,b). Wardle & Salmeron (2011) find that the Ohmic resistivity term provides an average value for the active layer surface density for a range of vertical magnetic fields.…”

Section: Layered Disc Modelmentioning

confidence: 99%

“…These suppress the ionization of the disc further leading to a larger dead zone (e.g. Bai & Goodman 2009; Bai & Stone 2011; Perez‐Becker & Chiang 2011a). The dead zone model should be investigated further in future work with respect to observations of transition discs.…”

Section: Transition Discsmentioning

confidence: 99%

Dead zones around young stellar objects: FU Orionis outbursts and transition discs

Martin

Lubow

Livio

et al. 2012

Monthly Notices of the Royal Astronomical Society

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We perform global time‐dependent simulations of an accretion disc around a young stellar object with a dead zone (a region where the magneto‐rotational instability cannot drive turbulence because the material is not sufficiently ionized). For infall accretion rates on to the disc of around 10−7 M⊙ yr−1, dead zones occur if the critical magnetic Reynolds number is larger than about 104. We model the collapse of a molecular gas cloud. At early times when the infall accretion rate is high, the disc is thermally ionized and fully turbulent. However, as the infall accretion rate drops, a dead zone may form if the critical magnetic Reynolds number is sufficiently large; otherwise the disc remains fully turbulent. With a dead zone the disc can become unstable to the gravo‐magneto instability. The mass of the star grows in large accretion outbursts that may explain FU Orionis events. At late times there is not sufficient mass in the disc for outbursts to occur but the dead zone becomes even more prominent as the disc cools. Large inner dead zones in the later stages of disc evolution may help to explain observations of transition discs with an inner hole.

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“…Turbulence driven by the magnetorotational instability (MRI; Balbus & Hawley 1991, 1998) is perhaps the most intensively studied mechanism. Recent studies explore a host of non-ideal magnetohydrodynamic effects that strongly affect the character of transport in poorly ionized disks (e.g., PerezBecker & Chiang 2011a, 2011bBai 2011;Wardle & Salmeron 2012;Bai & Stone 2013;Bai 2013;Simon et al 2013aSimon et al , 2013bKunz & Lesur 2013;Lesur et al 2014). Disk self-gravity is another option for sufficiently massive disks (e.g., Paczynski 1978;Gammie 2001;Forgan et al 2012).…”

Section: Introductionmentioning

confidence: 99%

Gravito-Turbulent Disks in Three Dimensions: Turbulent Velocities Versus Depth

Shi

Chiang

2014

ApJ

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Characterizing turbulence in protoplanetary disks is crucial for understanding how they accrete and spawn planets. Recent measurements of spectral line broadening promise to diagnose turbulence, with different lines probing different depths. We use three-dimensional local hydrodynamic simulations of cooling, self-gravitating disks to resolve how motions driven by "gravito-turbulence" vary with height. We find that gravito-turbulence is practically as vigorous at altitude as at depth. Even though gas at altitude is much too rarefied to be itself self-gravitating, it is strongly forced by self-gravitating overdensities at the midplane. The long-range nature of gravity means that turbulent velocities are nearly uniform vertically, increasing by just a factor of two from midplane to surface, even as the density ranges over nearly three orders of magnitude. The insensitivity of gravito-turbulence to height contrasts with the behavior of disks afflicted by the magnetorotational instability (MRI); in the latter case, noncircular velocities increase by at least a factor of 15 from midplane to surface, with various non-ideal effects only magnifying this factor. The distinct vertical profiles of gravito-turbulence versus MRI turbulence may be used in conjunction with measurements of non-thermal linewidths at various depths to identify the source of transport in protoplanetary disks.

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Surface Layer Accretion in Transitional and Conventional Disks: From Polycyclic Aromatic Hydrocarbons to Planets

Cited by 93 publications

References 98 publications

Nebular dead zone effects on the D/H ratio in chondrites and comets

Nebular dead zone effects on the D/H ratio in chondrites and comets

Dead zones around young stellar objects: FU Orionis outbursts and transition discs

Gravito-Turbulent Disks in Three Dimensions: Turbulent Velocities Versus Depth

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