The imprint of photoevaporation on edge-on discs

Abstract

We have performed hydrodynamic and radiative transfer calculations of a photoevaporating disc around a Herbig Ae/Be star to determine the evolution and observational impact of dust entrained in the wind. We find that the wind selectively entrains grains of different sizes at different radii resulting in a dust population that varies spatially and increases with height above the disc at radii >10 au. This variable grain population results in a 'wingnut' morphology to the dust density distribution. We calculate images of this dust distribution at near-infrared wavelengths that also show a 'wingnut' morphology at all wavelengths considered. We have also considered the contribution that crystalline dust grains will have in the wind and show that photoevaporative wind can result in a significant crystallinity fraction at all radii, when the disc is edge-on. However, when the disc's photosphere is unobscured, the photoevaporative wind makes no contribution to the observable crystallinity fraction in the disc. Finally, we conclude that the analysis of extended emission around edge-on discs could provide a new and independent method of testing photoevaporation models. © 2010 The Authors Monthly Notices of the Royal Astronomical Society © 2010 RAS.