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Register a new userObservable scattered light features from inclined and non-inclined planets embedded in protoplanetary discs
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Over the last few years instruments such as VLT/SPHERE and Subaru/HiCIAO have been able to take detailed scattered light images of protoplanetary discs. Many of the features observed in these discs are generally suspected to be caused by an embedded planet, and understanding the cause of these features requires detailed theoretical models. In this work we investigate disc-planet interactions using the PLUTO code to run 2D and 3D hydrodynamic simulations of protoplanetary discs with embedded 30 M$_{oplus}$ and 300 M$_{oplus}$ planets on both an inclined ($i = 2.86^{circ}$) and non-inclined orbit, using an $alpha$-viscosity of $4 times 10^{-3}$. We produce synthetic scattered-light images of these discs at emph{H-band} wavelengths using the radiative transfer code RADMC3D. We find that while the surface density evolution in 2D and 3D simulations of inclined and non-inclined planets remain fairly similar, their observational appearance is remarkably different. Most of the features seen in the synthetic emph{H-band} images are connected to density variations of the disc at around 3.3 scale heights above and below the midplane, which emphasizes the need for 3D simulations. Planets on sustained orbital inclinations disrupt the discs upper-atmosphere and produce radically different observable features and intensity profiles, including shadowing effects and intensity variation in the order of 10-20 times the surrounding background. The vertical optical depth to the disc midplane for emph{H-band} wavelengths is $tau approx 20$ in the disc gap created by the high-mass planet. We conclude that direct imaging of planets embedded in the disc remains difficult to observe, even for massive planets in the gap.
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We study the three-dimensional evolution of a viscous protoplanetary disc which accretes gas material from a second protoplanetary disc during a close encounter in an embedded star cluster. The aim is to investigate the capability of the mass accretion scenario to generate strongly inclined gaseous discs which could later form misaligned planets. We use smoothed particle hydrodynamics to study mass transfer and disc inclination for passing stars and circumstellar discs with different masses. We explore different orbital configurations to find the parameter space which allows significant disc inclination generation. citet{Thi2011} suggested that significant disc inclination and disc or planetary system shrinkage can generally be produced by the accretion of external gas material with a different angular momentum. We found that this condition can be fullfilled for a large range of gas mass and angular momentum. For all encounters, mass accretion from the secondary disc increases with decreasing mass of the secondary proto-star. Thus, higher disc inclinations can be attained for lower secondary stellar masses. Variations of the secondary discs orientation relative to the orbital plane can alter the disc evolution significantly. The results taken together show that mass accretion can change the three-dimensional disc orientation significantly resulting in strongly inclined discs. In combination with the gravitational interaction between the two star-disc systems, this scenario is relevant for explaining the formation of highly inclined discs which could later form misaligned planets.
We study the interaction between massive planets and a gas disc with a mass in the range expected for protoplanetary discs. We use SPH simulations to study the orbital evolution of a massive planet as well as the dynamical response of the disc for planet masses between 1 and $6 rmn{M_J}$ and the full range of initial relative orbital inclinations. Gap formation can occur for planets in inclined orbits. For given planet mass, a threshold relative orbital inclination exists under which a gap forms. At high relative inclinations, the inclination decay rate increases for increasing planet mass and decreasing initial relative inclination. For an initial semi-major axis of 5 AU and relative inclination of $i_0=80^circ,$ the times required for the inclination to decay by $10^circ$ is $sim10^{6} rmn{yr}$ and $sim10^{5} rmn{yr}$ for $1 rmn{M_J}$ and $6 rmn{M_J}$. Planets on inclined orbits warp the disc by an extent that is negligible for $1 rmn{M_J}$ but increases with increasing mass becoming quite significant for a planet of mass $6 rmn{M_J}$. We also find a solid body precession of both the total disc angular momentum vector and the planet orbital momentum vector about the total angular momentum vector. Our results illustrate that the influence of an inclined massive planet on a protoplanetary disc can lead to significant changes of the disc structure and orientation which can in turn affect the orbital evolution of the planet significantly.
We study the three-dimensional evolution of a viscous protoplanetary disc which is perturbed by a passing star on a parabolic orbit. The aim is to test whether a single stellar flyby is capable to excite significant disc inclinations which would favour the formation of so-called misaligned planets. We use smoothed particle hydrodynamics to study inclination, disc mass and angular momentum changes of the disc for passing stars with different masses. We explore different orbital configurations for the perturbers orbit to find the parameter spaces which allow significant disc inclination generation. Prograde inclined parabolic orbits are most destructive leading to significant disc mass and angular momentum loss. In the remaining disc, the final disc inclination is only below $20^circ$. This is due to the removal of disc particles which have experienced the strongest perturbing effects. Retrograde inclined parabolic orbits are less destructive and can generate disc inclinations up to $60^circ$. The final disc orientation is determined by the precession of the disc angular momentum vector about the perturbers orbital angular momentum vector and by disc orbital inclination changes. We propose a sequence of stellar flybys for the generation of misalignment angles above $60^circ$. The results taken together show that stellar flybys are promising and realistic for the explanation of misaligned Hot Jupiters with misalignment angles up to 60degr.
Three-dimensional 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 a less than a degree to the outer disc is indeed able to cast a shadow at larger radii. In our simulations a planet of around 6 Jupiter masses inclined by around 2 degrees is enough to warp the disc and cast a shadow with a depth of more than 10% of the average flux at that radius. We also demonstrate that 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 an recently observed shadow in the outer disc. Consideration of the observational constraints suggest that an inner disc precessing due to a misaligned planet is an unlikely explanation for the features found in TW Hya.
We study gap formation in gaseous protoplanetary discs by a Jupiter mass planet. The planets orbit is circular and inclined relative to the midplane of the disc. We use the impulse approximation to estimate the gravitational tidal torque between the planet and the disc, and infer the gap profile. For low-mass discs, we provide a criterion for gap opening when the orbital inclination is $leq 30^{circ}$. Using the FARGO3D code, we simulate the disc response to an inclined massive planet. The dependence of the depth and width of the gap obtained in the simulations on the inclination of the planet is broadly consistent with the scaling laws derived in the impulse approximation. Although we mainly focus on planets kept on fixed orbits, the formalism permits to infer the temporal evolution of the gap profile in cases where the inclination of the planet changes with time. This study may be useful to understand the migration of massive planets on inclined orbit, because the strength of the interaction with the disc depends on whether a gap is opened or not.
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