SUBSTRUCTURES IN PROTOPLANETARY DISCS - DUST AND GAS DYNAMICS

In this Thesis I have investigated a problem of great interest in the present star and planet formation research field: the characterization of substructures recently detected in protoplanetary discs. The goal of my work is to understand what physical processes induce the peculiar disc substructures observed to date in protoplanetary discs. In the first part of my work I investigate if the occurrence of local pressure maxima induced by gravitational instabilities can trap dust particles and explore the detectability of these inhomogeneities at near-infrared and (sub-) millimetre wavelengths. The observational predictions of the resulting models show that the resolution capabilities and sensitivity of current telescopes are sufficient to spatially resolve the peculiar spiral structure of gravitationally unstable discs. In the second part of my work I explore the dynamical clearing mechanism induced by forming protoplanets embedded in discs with the aim, on the one hand, of understanding the physics of dust gap opening and, on the other hand, of reproducing the gap-like structures observed in the disc around HL Tau. I provide a necessary and sufficient condition for the minimum planet mass able to carve a dust gap, as well as an estimate of the location of the outer edge of the dust gap, which can be useful to estimate the mass of the planet from high-resolution (sub-) millimetre observations. I apply my findings to the case of HL Tau, showing that the three gaps detected by ALMA can be described by the presence of sub-Jupiter mass planets. Finally, in the last part of my work, I investigate if the horseshoes observed at (sub-) millimetre wavelengths in transitional discs can be explained by the dynamics of gas and dust at the edge of the cavity carved by a binary object. I found that the cavities carved by binaries with large mass ratio becomes eccentric, leading to a horseshoe-like feature in the gas density and also in the dust surface density that can be detected with current telescopes. Although a variety of disc models can potentially reproduce the disc substructures observed to date in protoplanetary discs, the analysis performed in this Thesis shows that my models can accurately reproduce the observational results and can be useful for shedding light on the mechanism responsible for the disc substructures.