Simulating dust in SPH: a new model or HL Tau
Recent long-baseline ALMA (Atacama Large Millimeter Array) observations revealed a striking pattern of bright and dark rings in the protoplanetary disc surrounding the young star HL Tau. Dipierro et al. (2015) provided one of the earliest explanation of this systems in terms of the interaction of the disc with three newly born planets. The aim of this study is to develop a new model for gas and dust distribution within this disc, taking into account the most recent observational constraints. This work is focused on identifying the mass of the planets able to carve gaps in HL Tau, in the three main ring-like structures observed by ALMA. In order to reproduce the observed structures, we performed global 3D smoothed hydrodynamics simulations of both gas and dust within a protoplanetary disc hosting planets. Moreover, we computed the expected emission of the disc model through radiative transfer simulations, simulating realistic ALMA observations of the adopted theoretical model in order to compare ALMA predictions with real data. However, we discovered that the hydrodynamics simulations are affected by a non-negligible degree of dust mass non-conservation, clearly visible at large radii and in the upper layers of the disc. We therefore derived a new implementation of the one-fluid method in the SPH code Phantom to simulate the dynamics of dust grains in gas protoplanetary discs. We revise and extend previously developed algorithms by computing the evolution of a new fluid quantity that produces a more accurate and numerically controlled evolution of the dust dynamics.