Browsing by Author "Liu, Shang-Fei"

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    Investigating the Early Evolution of Planetary Systems with ALMA and the Next Generation Very Large Array
    (IOP Publishing, 2018) Ricci, Luca; Liu, Shang-Fei; Isella, Andrea; Li, Hui
    We investigate the potential of the Atacama Large Millimeter/submillimeter Array (ALMA) and the Next Generation Very Large Array (ngVLA) to observe substructures in nearby young disks which are due to the gravitational interaction between disk material and planets close to the central star. We simulate the gas and dust dynamics in the disk using the LA-COMPASS hydrodynamical code. We generate synthetic images for the dust continuum emission at submillimeter to centimeter wavelengths and simulate ALMA and ngVLA observations. We explore the parameter space of some of the main disk and planet properties that would produce substructures that can be visible with ALMA and the ngVLA. We find that ngVLA observations with an angular resolution of 5 milliarcsec at 3 mm can reveal and characterize gaps and azimuthal asymmetries in disks hosting planets with masses down to $\approx 5\,{M}_{\oplus }\approx 1\mbox{--}5\,\mathrm{au}$ from a solar-like star in the closest star-forming regions, whereas ALMA can detect gaps down to planetary masses of $\approx 20\,{M}_{\oplus }$ at 5 au. Gaps opened by super-Earth planets with masses $\approx 5\mbox{--}10\,{M}_{\oplus }$ are detectable by the ngVLA in the case of disks with low viscosity ($\alpha \sim {10}^{-5}$) and low pressure scale height (h ≈ 0.025 au at 5 au). The ngVLA can measure the proper motion of azimuthal asymmetric structures associated with the disk–planet interaction as well as possible circumplanetary disks on timescales as short as one to a few weeks for planets at 1–5 au from the star.
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    New Constraints on Turbulence and Embedded Planet Mass in the HD 163296 Disk from Planet–Disk Hydrodynamic Simulations
    (IOP Publishing, 2018) Liu, Shang-Fei; Jin, Sheng; Li, Shengtai; Isella, Andrea; Li, Hui
    Recent Atacama Large Millimeter and Submillimeter Array (ALMA) observations of the protoplanetary disk around the Herbig Ae star HD 163296 revealed three depleted dust gaps at 60, 100, and 160 au in the 1.3 mm continuum as well as CO depletion in the middle and outer dust gaps. However, no CO depletion was found in the inner dust gap. To examine the planet–disk interaction model, we present results of 2D two fluid (gas + dust) hydrodynamic simulations coupled with 3D radiative transfer simulations. To fit the high gas-to-dust ratio of the first gap, we find that the Shakura–Sunyaev viscosity parameter α must be very small ($\lesssim {10}^{-4}$) in the inner disk. On the other hand, a relatively large α ($\sim 7.5\times {10}^{-3}$) is required to reproduce the dust surface density in the outer disk. We interpret the variation of α as an indicator of the transition from an inner dead zone to the outer magnetorotational instability (MRI) active zone. Within ~100 au, the HD 163296 disk's ionization level is low, and non-ideal magnetohydrodynamic effects could suppress the MRI, so the disk can be largely laminar. The disk's ionization level gradually increases toward larger radii, and the outermost disk ($r\gt 300$ au) becomes turbulent due to MRI. Under this condition, we find that the observed dust continuum and CO gas line emissions can be reasonably fit by three half-Jovian-mass planets (0.46, 0.46, and $0.58\,{M}_{{\rm{J}}}$) at 59, 105, and 160 au, respectively.