Search

We present a method for simulating the dynamics of a mixture of gas and multiple species of large Stokes number dust grains, typical of evolved protoplanetary discs and debris discs. The method improves upon earlier methods, in which only a single grain size could be represented, by capturing the differential backreaction of multiple dust species on the gas. This effect is greater for large dust-to-gas ratios that may be expected in the later stages of the protoplanetary disc life. We benchmark the method against analytic solutions for linear waves, drag, and shocks in dust–gas mixtures, and radial drift in a protoplanetary disc showing that the method is robust and accurate. [ABSTRACT FROM AUTHOR]

Tidal encounters in star clusters perturb discs around young protostars. In Cuello et al. we detailed the dynamical signatures of a stellar flyby in both gas and dust. Flybys produce warped discs, spirals with evolving pitch angles, increasing accretion rates, and disc truncation. Here, we present the corresponding observational signatures of these features in optical/near-infrared scattered light and (sub) millimetre continuum and CO line emission. Using representative prograde and retrograde encounters for direct comparison, we post-process hydrodynamical simulations with radiative transfer methods to generate a catalogue of multiwavelength observations. This provides a reference to identify flybys in recent near-infrared and submillimetre observations (e.g. RW Aur, AS 205, HV Tau and DO Tau, FU Ori, V2775 Ori, and Z CMa). [ABSTRACT FROM AUTHOR]

3D hydrodynamic numerical simulations have demonstrated that the structure of a protoplanetary disc may be strongly affected by a planet orbiting in a plane that is misaligned to the disc. When the planet is able to open a gap, the disc is separated into an inner, precessing disc and an outer disc with a warp. In this work, we compute infrared scattered light images to investigate the observational consequences of such an arrangement. We find that an inner disc misaligned by less than a degree to the outer disc is indeed able to cast a shadow at larger radii. In our simulations, a planet of |${\gtrsim }6\, M_{\rm J}$| inclined by ≳2° is enough to warp the disc and cast a shadow with a depth of |${\gtrsim } 10{{\ \rm per\ cent}}$| of the average flux at that radius. We also demonstrate that the warp in the outer disc can cause a variation in the azimuthal brightness profile at large radii. Importantly, this latter effect is a function of the distance from the star and is most prominent in the outer disc. We apply our model to the TW Hya system, where a misaligned, precessing inner disc has been invoked to explain a recently observed shadow in the outer disc. Consideration of the observational constraints suggests that an inner disc precessing due to a misaligned planet is an unlikely explanation for the features found in TW Hya. [ABSTRACT FROM AUTHOR]

We test the hypothesis that the sub-millimetre thermal emission and scattered light gaps seen in recent observations of TW Hya are caused by planet–disc interactions. We perform global three-dimensional dusty smoothed particle hydrodynamics simulations, comparing synthetic observations of our models with dust thermal emission, CO emission, and scattered light observations. We find that the dust gaps observed at 24 au and 41 au can be explained by two super-Earths (∼ 4 M⊕). A planet of approximately Saturn-mass can explain the CO emission and the depth and width of the gap seen in scattered light at 94 au. Our model produces a prominent spiral arm while there are only hints of this in the data. To avoid runaway growth and migration of the planets we require a disc mass of |${\lesssim } 10^{-2}\, \mathrm{M}_{\odot }{}$| in agreement with CO observations but 10–100 times lower than the estimate from HD line emission. [ABSTRACT FROM AUTHOR]

We present 3D smoothed particle hydrodynamics simulations of protoplanetary discs undergoing a flyby by a stellar perturber on a parabolic orbit lying in a plane inclined relative to the disc mid-plane. We model the disc as a mixture of gas and dust, with grains ranging from 1  |$\mu$| m to 10 cm in size. Exploring different orbital inclinations, periastron distances, and mass ratios, we investigate the disc dynamical response during and after the flyby. We find that flybys induce evolving spiral structure in both gas and dust that can persist for thousands of years after periastron. Gas and dust structures induced by the flyby differ because of drag-induced effects on the dust grains. Variations in the accretion rate by up to an order of magnitude occur over a time-scale of the order of 10 yr or less, inducing FU Orionis-like outbursts. The remnant discs are truncated and warped. The dust disc is left more compact than the gas disc, both because of disc truncation and accelerated radial drift of grains induced by the flyby. [ABSTRACT FROM AUTHOR]

We present 3D hydrodynamical models of the HD142527 protoplanetary disc, a bright and well-studied disc that shows spirals and shadows in scattered light around a 100 au gas cavity, a large horseshoe dust structure in mm continuum emission, together with mysterious fast radial flows and streamers seen in gas kinematics. By considering several possible orbits consistent with the observed arc, we show that all of the main observational features can be explained by one mechanism - the interaction between the disc and the observed binary companion. We find that the spirals, shadows, and horseshoe are only produced in the correct position angles by a companion on an inclined and eccentric orbit approaching periastron - the 'red' family from Lacour et al. Dust-gas simulations show radial and azimuthal concentration of dust around the cavity, consistent with the observed horseshoe. The success of this model in the HD142527 disc suggests other mm-bright transition discs showing cavities, spirals, and dust asymmetries may also be explained by the interaction with central companions. [ABSTRACT FROM AUTHOR]