Oral title: Probing dust and gas evolution in protoplanetary disks. The pivotal Chamaeleon II association.

Oral abstract: In the context of planetary formation, the formation and evolution of a disk around a young star seems to be 
one of the major steps. Several mechanisms drive the evolution and dispersal of disks and each of them will have an 
impact on the appearance of the protoplanetary disks, hence, on our capacity to extract direct observational constraints. 
Constraining disk evolutional lifetime is essential to understand mechanisms at play, in particular planet formation that 
has to happen before the disk has dissipated.
We studied a sample of 31 protoplanetary disks in the Chamaeleon II dark cloud, using ALMA Cycle 2 data (age of 4 ± 2 
Myr). We characterize dust fluxes, sizes and masses, and compare them to the gas ones. Then, by comparing our 
results to those in other star forming regions, such as Lupus (∼ 1 − 3 Myr) or Upper Sco (∼ 11 Myr), we constrain the 
typical disk mass evolution timescales in different environments and find a typical value of ~1.5 Myr. From cumulative 
mass distributions for differently aged star forming regions, we find that disks in old regions seems to be lighter than 
disks located in younger regions. Considering gas evolution by comparing [OI] or CO isotopologues detections rates in 
several star forming regions, we found that old regions seems to have less gas than younger regions, in accordance to 
disks dissipation models. We also inferred that gas seems to dissipate faster than dust.