A Global Hydrodynamic Investigation into the Transport of Material in Protoplanetary Discs

Abstract

Recent advancements in planet formation theory have highlighted pebble accretion as a crucial process, offering a solution to the meter-sized barrier in dust growth and significantly reducing timescales in core accretion models. This efficient growth mechanism enables the formation of massive planets within disc lifetimes, addressing a key challenge in traditional core accretion scenarios. Our study investigates the influence of massive planets on gas and dust motion in protoplanetary discs, with a focus on material transport through planetary- induced gaps. Using 3D global hydrodynamic simulations with FARGO3D, we explore dust filtration and transport in discs with embedded planets with masses equal to or exceeding the pebble isolation mass, i.e., masses large enough to prevent ~mm sized dust grains from moving through a planetary-induced gap. Our findings reveal that material available for further planetary growth in the inner disc primarily consists of pre-existing inner disc material, along with gas and small dust grains that permeate through the gap from the outer disc. Notably, dust and gas entering the planet-carved gap originate near the mid-plane and pass through the planet’s Hill sphere, experiencing significant temperature increases. In the case of a Jupiter-mass planet at ~ 100 AU, this implies likely CO ice desorption from grains in close proximity to the planet. Further exploration of the parameter space demonstrates that a basic approximation of filtration can be obtained comparing the planet mass to the corresponding pebble isolation mass for the disc aspect ratio, with similar results obtained for planets of equivalent mass ratios. With low optical depths to these planets placed at 100 AU at 1 mm and 1 μm wavelengths, the dust studied here is unlikely to impact on the detectability. However, when placing our disc at a distance of 140 parsec, the circumplanetary discs of these embedded planets remain likely unobservable in ALMA Bands 6 and 7. This theoretical work, set against the backdrop of recent progress in protoplanet detection therefore offers valuable contributions to our understanding of material dynamics in these discs. By modelling the impact of massive planets on disc dynamics, this work enriches our understanding of the physical processes in planet formation and protoplanetary disc evolution.