The Structure of Extrasolar Planetesimal Belts in Images

Abstract

Solid bodies in the form of planets and planetesimal belts familiar to us in the Solar System are also a prevalent feature around other stars. Their great diversity highlights a lack of complete theories for how they formed, which is further complicated by observational challenges to understand their full architecture in the first place. Currently, our best observational constraints on the outer planetary system come from imaging the planetesimal belts that population this region, known as debris disks. As planets dynamically interact with the disk throughout their formation and evolution, structures reflecting their history are imprinted on the disk. In this thesis, I develop systematic and unbiased methods to recover the three-dimensional structure of debris disks from their images applicable to a versatile range of imaging modes. By removing assumptions on the functional form of the disk structure, this method provides unbiased constraints on disk substructures with realistic uncertainties that enable us to interpret dynamical interactions shaping the planetary system. I apply this method to a sample of debris disks with resolved imaging to infer general three-dimensional structures of debris disks and their implications for planetary system formation. For the archetypal edge-on debris disk of $\beta$ Pictoris for which multiple epochs of high-resolution mid-infrared and millimetre images are available, I model in detail its vertical structure for different grain sizes and any variations in azimuthal substructures across time, constraining dynamical scenarios that could be shaping the evolution of the system. The approaches developed in this work to model debris disk structures from images will be important for interpreting upcoming observations with ALMA, JWST and the next generation of observatories at high sensitivity and resolution.