The dispersal of protoplanetary discs I: A new generation of X-ray photoevaporation models

Abstract

Photoevaporation of planet forming discs by high energy radiation from the central star is potentially a crucial mechanism for disc evolution and it may play an important role in the formation and evolution of planetary system. We present here a new generation of X-ray photoevaporation models for solar-type stars, based on a new set of hydrodynamical simulations, which account for stellar irradiation via a new, significantly improved, parameterisation of gas temperatures, based on detailed photoionisation and radiation transfer calculations. This is the first of a series of papers aiming at providing a library of models which cover the observed parameter space in stellar and disc mass, metallicity and stellar X-ray properties. We focus here on solar-type stars (0.7 M$_\odot$) with relatively low-mass discs (1% of the stellar mass) and explore the dependence of the wind mass loss rates on stellar X-ray luminosity. We model primordial discs as well as transition discs at various stages of evolution. Our 2D hydrodynamical models are then used to derive simple recipes for the mass loss rates that are suitable for inclusion in one-dimensional disc evolution and/or planet formation models typically employed for population synthesis studies. Line profiles from typical wind diagnostics ([OI] 6300 $\overset{\lower.5em\circ}{\mathrm{A}}$ and [NeII] 12.8 $μ$m) are also calculated for our models and found to be roughly in agreement with previous studies. Finally, we perform a population study of transition discs by means of one-dimensional viscous evolution models including our new photoevaporation prescription and find that roughly a half of observed transition discs cavities and accretion rates could be reproduced by our models.