Interferometric observations to analyze circumstellar environments and planetary formation

Protoplanetary disks have a rich structure, with different physics playing a role in different regions of the disk. They are under constant evolution, due to a combination of various physical and chemical processes, e.g., accretion, photo-evaporation, gas-dust interactions, grain growth, and the interaction with protoplanets. The dynamic ranges involved span orders of magnitudes on spatial scales, orbital times, temperatures, and dust- or gas-densities. The extreme dynamic ranges involved in the structure and composition of these objects mean that very different observational techniques have to be combined together to probe their various regions. This work makes use of new interferometric and spectroscopic measurements in the infrared, together with published mid-infrared images and spectral energy distribution fluxes from UV to mm-wavelength, to instruct a new comprehension of the well-known IRS48 object, and uncover part of the delicate balance of physical processes at stake. This PhD reports the first direct imaging of the full extents of a polycyclic aromatic hydrocarbon and very small grains ring in a young circumstellar disk, presents a revised model for the IRS48 object to explain the rich and complex dust- and gas-environment observed from near-infrared to centimeter wavelengths. Also, the spectral type of the spectroscopic binary MWC361 is determined. This will lead to a precise characterization of the stellar parameters of this binary, opening a new window on the studying of the disappearance of the circumsecondary disk of the binary, while the circumprimary disk is still present. The leitmotif throughout this thesis is the understanding of the last moments of circumstellar disks, and the search for the processes which dissipate them. This particular step of the disk-evolution is one the most mysterious to date, yet it sets critical constraints on the by-product of circumstellar disks, exoplanets