From dust to planets: high resolution observations of small-scale structures in evolving protoplanetary disks

This thesis work aimed at studying the first stages planet formation, focusing on protoplanetary disks of gas and dust around pre-main sequence stars. During their relatively short life (≥ 5 Million years) disks are expected to give origin to large solid bodies and planets, but the mechanisms and timescales of these process are still not well constrained. In particular, the so called "core accretion" scenario predicts that dust grains stick together via direct collisions and form larger aggregates up to planetesimals sizes; but both simulations and laboratory experiments show that grain growth should be hindered by two main mechanisms, the first leading to destructive outcomes when grains collide beyond a certain size/velocity ("fragmentation barrier"), the second removing bigger grains as a consequence of the aerodynamical drag that the gas exerts on the dust ("drift barrier"). The fact that we observe large grains in several protoplanetary disks, and the evidence of a large number of extrasolar planetary systems, suggest that there must be other mechanisms that promote grain growth, overcoming these two main barriers. In this framework I focused on studying disk evolution through high resolution observations taken with new-generation radio intreferometers, with the purpose of obtaining a better understanding of the mechanisms driving dust growth and ultimately planet formation.