This thesis presents a comprehensive investigation of the properties of protoplanetary disks, the birthplaces of planets. This work is motivated by the rapidly
increasing quality of observational data, which necessitates better theories and
ways to compare them with what we observe.
Firstly, we showcase how the size of the millimeter continuum emitting region
constrains disk masses. We assess the method’s efficacy by conducting detailed
dust evolution calculations and considering diverse disk properties, particularly in
disks exhibiting radial substructures.
We then constrain the disk dust grain size distribution by observing only the
largest and smallest grains within it. Merging physical dust models with radiative
transfer calculations, we compare the model outcomes with the observations of
the IM Lup disk, revealing a segregated grain size distribution and providing new
insight into grain formation mechanisms and potential triggers for planetesimal
formation.
Additionally, we characterize the inner disk of the very low-mass star 2MASSJ16053215-1933159 through atomic and molecular hydrogen lines. Using the observational capabilities of the James Webb Space Telescope (JWST), we measure
gas temperature, mass, and the stellar accretion rate while showcasing JWST
potential in the characterization of protoplanetary disk structures.
Lastly, we investigate the gas density and temperature across Class II protoplanetary disks in Taurus using the NOEMA instrument. Employing machine learning-enhanced chemistry and analyzing optically thin and thick CO isotopologue emission, we successfully constrain disk masses and temperatures
