Dust survival in harsh environments

Abstract

Aims. We investigate the role of photo-evaporation of dust that is exposed to the radiation field of hot young stars and planetary nebulae (PNe) as a possible destruction mechanism of dust grains in the interstellar medium (ISM). Methods. We estimated photo-evaporation induced by the feedback of individual or clustered young stars, of PNe, and in the presence of a variable radiation field that scales with the interstellar radiation field. For PNe, we investigated the dust photo-evaporation of dust grains already present in the ISM and of those formed in the last phases of the evolution of thermally pulsing asymptotic giant branch (TP-AGB) stars. We included dust photo-evaporation rate in models of dust evolution in galaxies for different assumptions of the dust growth scenario, the dust-to-gas ratios, the star formation histories, and the initial mass functions of the stars. Results. For all the cases we considered, we found that both photo-evaporation from young stars and from PNe is negligible with respect to other dust-removal processes such as destruction from supernova shocks, astration, and possibly outflow. Grains are stable against photo-evaporation when they are exposed to a radiation field that is up to 107 times the interstellar radiation field. Conclusions. Dust grains of size ≥0.01 µm are not efficiently destroyed either by photo-evaporation in the presence of a strong radiation field.