Dispersal of protoplanetary discs: how stellar properties and the local environment determine the pathway of evolution

We study the evolution and final dispersal of protoplanetary discs that evolve under the action of internal and external photoevaporation, and different degrees of viscous transport. We identify five distinct dispersal pathways, which are (i) very long-lived discs (> 20 Myr), (ii) inside-out dispersal where internal photoevaporation dominates and opens inner holes, (iii) outside-in dispersal where external photoevaporation dominates through disc truncation, and two intermediate regimes characterized by lingering material in the inner disc with the outer disc dispersed predominantly by either internal or external photoevaporation. We determine how the lifetime, relative impact of internal and external winds, and clearing pathway vary over a wide, plausible, parameter space of stellar/disc/radiation properties. There are a number of implications, for example, in high UV environments because the outer disc lifetime is shorter than the time-scale for clearing the inner disc, we do not expect transition discs to be common, which appears to be reflected in the location of transition disc populations towards the Orion Nebular Cluster. Irrespective of environment, we find that ongoing star formation is required to reproduce observed disc fractions as a function of stellar cluster age. This work demonstrates the importance of including both internal and external winds for understanding protoplanetary disc evolution.

Automated summary

This study explores the evolution and dispersal of protoplanetary discs under the influence of internal and external photoevaporation and varying degrees of viscous transport. It identifies five distinct dispersal pathways and shows that the relative impact of internal and external winds, as well as the clearing pathway, vary with different stellar/disc/radiation properties. The study highlights the importance of considering both internal and external winds in understanding protoplanetary disc evolution.