Gaps, rings, and non-axisymmetric structures in protoplanetary disks: Emission from large grains

Abstract

Aims. Dust grains with sizes around (sub)mm are expected to couple only weakly to the gas motion in regions beyond 10 au of circumstellar disks. In this work, we investigate the influence of the spatial distribution of these grains on the (sub)mm appearance of magnetized protoplanetary disks. Methods. We perform non-ideal global 3D magneto-hydrodynamic (MHD) stratified disk simulations, including particles of different sizes (50 µm to 1 cm), using a Lagrangian particle solver. Subsequently, we calculate the spatial dust temperature distribution, including the dynamically coupled submicron-sized dust grains, and derive ideal continuum re-emission maps of the disk through radiative transfer simulations. Finally, we investigate the feasibility of observing specific structures in the thermal re-emission maps with the Atacama Large Millimeter/submillimeter Array (ALMA). Results. Depending on the level of turbulence, the radial pressure gradient of the gas, and the grain size, particles settle to the midplane and/or drift radially inward. The pressure bump close to the outer edge of the dead-zone leads to particle-trapping in ring structures. More specifically, vortices in the disk concentrate the dust and create an inhomogeneous distribution of solid material in the azimuthal direction. The large-scale disk perturbations are preserved in the (sub)mm re-emission maps. The observable structures are very similar to those expected from planet-disk interaction. Additionally, the larger dust particles increase the brightness contrast between the gap and ring structures. We find that rings, gaps, and the dust accumulation in the vortex could be traced with ALMA down to a scale of a few astronomical units in circumstellar disks located in nearby star-forming regions. Finally, we present a brief comparison of these structures with those recently found with ALMA in the young circumstellar disks of HL Tau and Oph IRS 48.

Radiation Hydrodynamical Turbulence in Protoplanetary Disks: Numerical Models and Observational Constraints

“…Further, we compared our models with observational constraints, and also with results from a magnetized disk model by Flock et al (2015) and Ruge et al (2016). The main findings are: The rest of the image is generated by applying periodic azimuthal boundary conditions.…”

“…The particle motion is solved using a Lagrangian method based on the equation of motion in the spherical coordinates system. For more details on the particle motion routine we refer to the Appendix section by Ruge et al (2016). We place a total of one million particles equally distributed over two sizes, and uniformly distributed in the r − φ plane at the midplane.…”

“…The dust density is sampled using 3 dust bins, the small grain bin with a smooth size distribution from 0.1µm to 10µm and two large grain bins with single sizes of 100µm and 1000µm. To distribute and sample the total dust mass over the bins we follow the prescription presented by Ruge et al (2016) (Appendix A therein) and using the power-law index of −3.5 to determine the size distribution. Fig.…”

Multiple Disk Gaps and Rings Generated by a Single Super-Earth

“…Simulations with a more realistic dust size distribution are a natural extension (e.g., Ruge et al 2016). In this work we chose 200 μm as a representative size for the "big" dust particles.…”

The Complex Morphology of the Young Disk MWC 758: Spirals and Dust Clumps around a Large Cavity

“…Gaps/Rings might be zonal-flows (Johansen et al 2009), self-induced dust pile-ups due to radial migration (Gonzalez et al 2015), pebble growth around condensation front (Zhang et al 2015), or gradient in the viscosity at the outer edge of a dead-zone (Regály et al 2012;Ruge et al 2016). Local dust concentrations might be vortices induced by a large range of instabilities such the baroclinic instability (Lesur & Papaloizou 2010) or the vertical shear instability (Nelson et al 2013), which do not require a planet.…”