Contribution Contributed Talk
Collisional modelling of the AU Mic debris disc
Being remnants of the planet formation process, debris discs consist of (invisible) planetesimals and collisionally-replenished dust. Observations from optical to submm wavelengths reveal their presence around at least 20% of main-sequence stars. Systems that are spatially resolved at multiple wavelengths and have densely sampled SEDs allow us to more tightly constrain the physical properties of debris discs. We performed an in-depth collisional modelling of the prominent debris disc around the young M star AU Mic, aiming at a comprehensive understanding of the dust production and the dynamics of the disc objects in this system. The simulations started from a distribution of planetesimals and followed the production and loss of material in a collisional cascade, including stellar radiative and stellar wind forces. Our models were compared to a suite of observational data for scattered light and thermal emission, ranging from polarisation measurements in the visible to the ALMA radial surface brightness profile at 1.3mm. Most of the data can be reproduced with a planetesimal distribution that has an outer edge at around 40au and possesses a low dynamical excitation. We find a preference for strong stellar winds and for dust grains that consist of a silicate-carbon mixture of moderate porosity. While the SED and the shape of the ALMA profile are well reproduced, the scattered light observations deviate from the models more strongly. This possibly indicates a shortcoming of the scattered light model by spherical grains used. We also discuss the origin of the unresolved central emission detected by ALMA and show that it cannot stem from an additional inner planetesimal belt alone.