DUST FILTRATION BY PLANET-INDUCED GAP EDGES: IMPLICATIONS FOR TRANSITIONAL DISKS

By Zhaohuan Zhu, R. Nelson, R. Dong, Catherine C. Espaillat, L. Hartmann. 2012

250 citations recorded by the source corpus.

By carrying out two-dimensional two-fluid global simulations, we have studied the response of dust to gap formation by a single planet in the gaseous component of a protoplanetary disk—the so-called dust filtration mechanism. We have found that a gap opened by a giant planet at 20 AU in an α = 0.01, disk can effectively stop dust particles larger than 0.1 mm drifting inward, leaving a submillimeter (submm) dust cavity/hole. However, smaller particles are difficult to filter by a gap induced by a several MJ planet due to (1) dust diffusion and (2) a high gas accretion velocity at the gap edge. Based on these simulations, an analytic model is derived to understand what size particles can be filtered by the planet-induced gap edge. We show that a dimensionless parameter Ts/α, which is the ratio between the dimensionless dust stopping time and the disk viscosity parameter, is important for the dust filtration process. Finally, with our updated understanding of dust filtration, we have computed Monte Carlo radiative transfer models with variable dust size distributions to generate the spectral energy distributions of disks with gaps. By comparing with transitional disk observations (e.g., GM Aur), we have found that dust filtration alone has difficulties depleting small particles sufficiently to explain the near-IR deficit of moderate transitional disks, except under some extreme circumstances. The scenario of gap opening by multiple planets studied previously suffers the same difficulty. One possible solution is to invoke both dust filtration and dust growth in the inner disk. In this scenario, a planet-induced gap filters large dust particles in the disk, and the remaining small dust particles passing to the inner disk can grow efficiently without replenishment from fragmentation of large grains. Predictions for ALMA have also been made based on all these scenarios. We conclude that dust filtration with planet(s) in the disk is a promising mechanism to explain submm observations of transitional disks but it may need to be combined with other processes (e.g., dust growth) to explain the near-IR deficit of some systems.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/59f490245cb3d5d2552f9139ee0f057cc4f77f8a

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In Astronomy and Astrophysics

1. T. Birnstiel
2. Anders Johansen
3. D. Wilner
4. S. Andrews
5. Xue-Ning Bai
6. Zhaohuan Zhu
7. C. Dullemond
8. A. Hughes

In Instrumentation

1. S. Andrews
2. T. Birnstiel
3. Xue-Ning Bai
4. Anders Johansen
5. D. Wilner
6. Zhaohuan Zhu
7. R. Dong
8. A. Hughes

Citations in the corpus

• Small vs. large dust grains in transitional disks: do different cavity sizes indicate a planet? - SAO 206462 (HD 135344B) in polarized light with VLT/NACO (2013, background): “However, Zhu et al. (2012) argued that dust filtration alone cannot explain the observed spectral deficit (invoking additional processes such as dust growth).”
• The Disk Substructures at High Angular Resolution Project (DSHARP). I. Motivation, Sample, Calibration, and Overview (2018, background): “…should substantially amplify the associated local mm/cm-sized particle density (e.g., Paardekooper & Mellema 2006; Rice et al. 2006; Pinilla et al. 2012b; Zhu et al. 2012), generating a bright signature in the broadband (sub-)mm continuum that is much easier to measure on the smallest scales.”
• Dust Evolution and the Formation of Planetesimals (2016, background): “Such vortices can trap dust particles (e.g., Barge & Sommeria 1995; Meheut et al. 2012; Lyra & Lin 2013; Raettig et al. 2015) in a similar way to pressure bumps (Paardekooper & Mellema 2004; Pinilla et al. 2012; Zhu et al. 2012; Birnstiel et al. 2013; Lyra & Lin 2013).”
• Observational Signatures of Planets in Protoplanetary Disks I: Gaps Opened by Single and Multiple Young Planets in Disks (2014, methodology): “This approximation is always true for our chosen particle size (more discussion and the detailed comparison with other approaches are given in the Appendix of Zhu et al. 2012).”
• The Disk Substructures at High Angular Resolution Project (DSHARP). VI. Dust Trapping in Thin-ringed Protoplanetary Disks (2018, methodology): “That would then be where the dust gets trapped (e.g. Rice et al. 2006; Zhu et al. 2012; Pinilla et al. 2012a).”
• Gaps and Rings in an ALMA Survey of Disks in the Taurus Star-forming Region (2018, background): “…(Neptune mass) embedded in the disk forms a gap in the gas density structure around its orbit, leading to the formation of a pressure bump outside the planet orbit, trapping large dust grains into rings and forming deep dust gaps (e.g., Lin & Papaloizou 1986; Pinilla et al. 2012a; Zhu et al. 2012).”
• Multiple Disk Gaps and Rings Generated by a Single Super-Earth (2017, background): “In particular, the edges of planet-opened gaps are regions of high gas pressure, and dust particles drift toward such regions and collect into overdense rings (e.g., Paardekooper & Mellema 2004, 2006; Zhu et al. 2012; Pinilla et al. 2012a).”
• OBSERVATIONAL SIGNATURES OF PLANETS IN PROTOPLANETARY DISKS: SPIRAL ARMS OBSERVED IN SCATTERED LIGHT IMAGING CAN BE INDUCED BY PLANETS (2015, methodology): “…simulations were post-processed via the 3D MCRT calculations using the code developed by Whitney et al. (2013), which has been used to model protoplanetary disks in the past (e.g., Dong et al. 2012a, 2012b, 2014; Hashimoto et al. 2012; Zhu et al. 2012; Follette et al. 2013; Grady et al. 2013).”
• HOW EMPTY ARE DISK GAPS OPENED BY GIANT PLANETS (2013, background): “…thin that planets alone seem incapable of torquing material strongly enough to compete with viscous diffusion — at least for typically assumed parameters — and appeals are made to opacity reductions through grain growth or dust filtration at the outer gap edge (Zhu et al. 2012; Dong et al. 2012).”
• The Disk Substructures at High Angular Resolution Project (DSHARP). VII. The Planet–Disk Interactions Interpretation (2018, background): “Dust turbulent diffusion with the large α can further smooth out dust features (Zhu et al. 2012).”