Characterizing the dust content in the outer regions of protoplanetary disks

Characterizing the dust content in the outer regions of protoplanetary disks Abstract: The dust mass budget of protoplanetary disks plays an important role in planet formation. However, ALMA surveys often underestimate disk masses, as many disks have extended low surface-brightness regions at hundreds of au that fall below ALMA's sensitivity limits. This may contribute to the mass-budget problem, where exoplanetary system masses appear comparable to or even greater than those of the most massive disks. In this poster, I will present our work on TW Hya, where we use image-plane retrieval as well as visibility-plane modelling on ALMA observations. We find a faint ring in the outer regions at multiple millimeter wavelengths, with a spectral index similar to that of the ISM. We aim to extend this study to other disks that exhibit flat intensity profiles in their outer regions and could potentially host a mass reservoir. Investigating their surface density, particle size distribution, and dust mass allows us to shed light on their origin. ELT instruments such as METIS will enable high sensitivity imaging of thermal emission from small grains in the outer disk, complementing ALMA at shorter wavelengths. Combined with high angular resolution scattered light observations from instruments like MICADO and HARMONI, the ELT will offer a powerful toolkit to characterize faint dust structures and constrain their composition and spatial distribution.