Photoevaporation of protoplanetary discs – II. Evolutionary models and observable properties

We present a new model for protoplanetary disc evolution. This model combines viscous evolution with photoevaporation of the disc. However, in a companion paper we have shown that at late times such models must consider the effect of stellar radiation directly incident on the inner disc edge, and here we model the observational implications of this process. We find that the entire disc is dispersed on a time-scale of the order of 105 yr after a disc lifetime of a few Myr, consistent with observations of T Tauri (TT) stars. We use a simple prescription to model the spectral energy distribution of the evolving disc, and demonstrate that the model is consistent with observational data across a wide range of wavelengths. We also note that the model predicts a short ‘inner hole’ phase in the evolution of all TT discs, and make predictions for future observations at mid-infrared and millimetre wavelengths.