Self-gravity is an essential ingredient to determine the dynamics of young, massive protoplanetary discs: their mass can be a considerable fraction of the stellar one, and the system may develop gravitational instability (GI). The characteristic signature of GI is the presence of a spiral perturbation, that deeply influences disc evolution, since it is the main driver of angular momentum transport.
GI spirals perturb the velocity field, leaving clear kinematic imprints in molecular line emission. These signatures, dubbed as “GI wiggles”, give insights about the strength of the instability, and hence the quantity of angular momentum redistributed thorough the disc. In this poster, we present a linear analytical theory for the GI wiggles, and then we apply this to measure the gravito-turbulent viscosity in the system Elias 2-27. We then compare the measured accretion rate of this system with the one obtained by the linear theory, finding an excellent agreement.