The hallmarks of internal photoevaporation in protoplanetary disc populations

The evolution of protoplanetary discs plays an important role in theories of planet formation. Two evolutionary models have been proposed so far, namely the viscous-photoevaporative paradigm and the MHD wind model, but to date none of them has been ruled out by observations. In the last decade, recent surveys have measured macroscopical properties in large samples of discs in various star-forming regions. Consequently, population synthesis can represent a powerful tool to distinguish the models in observed populations. In my project, I am studying the properties of discs populations where viscosity drives accretion and internal photoevaporation is responsible for disc dispersal. I derive a new analytical relation to choose the disk initial conditions to reproduce the observed disc fraction. Furthermore, I find that the median of the mass distribution of survived discs increases with the age of the population. This feature is counter-intuitive since the mass of each single disc decreases with time and is due to photoevaporation dispersing less massive discs first in populations. I find that this behaviour occurs in an idealized case, where the wind mass-loss rate is independent on the stellar mass, but also when one imposes commonly observed power law correlations between the initial conditions and the stellar mass. I will show both the results obtained with the population synthesis code “Diskpop” and an analytical framework to interpret such features. Since such behaviour is not expected in the MHD wind model, it can potentially represent a method to distinguish the viscous-photoevaporative model in observed populations.