An Investigation of the Streamline Geometry of Photoevaporative Winds from Planet-Forming Disks

Abstract:

The evolution and dissipation of viscously accreting protoplanetary disks is a key element in understanding the formation of planetary systems. By investigating the timescales on which circumstellar disks are dispersed by photoevaporation from the central star, as well as the quantities and types of materials that remain, conclusions may be drawn regarding the likelihood of planet formation in the modeled disk system. Through the use of a one-dimensional viscous diffusion model for the disk, the photoevaporative dispersal of the disk mass is investigated under varied conditions. In this model, the dust and gas components are treated separately, and the effects of far-ultraviolet, extreme-ultraviolet, and x-ray irradiation are considered.

In this investigation, the surface density is affected by dynamics of the photoevaporative wind, of which different streamline models will be utilized (in addition to a control case with no wind calculation.) We present comparisons of the disk evolution and dispersion under these differing wind models in order to determine which results are in best agreement with observations, as well as to investigate the extent to which the streamline geometry affects photoevaporative mass loss rates and resulting disk lifetimes. Furthermore, we seek to explore the spatial distribution of remaining solids following the dispersal of the disk for each wind case. The spatial distribution and abundance of disk solids may determine the radial zones where comets, meteorites, and planetesimals may form in the wake of the dispersed disk. Additional inquiries for these differing wind conditions include: investigating line profiles of escaping gases, study of the evolving composition of remnant disk gas (an indicator of potential giant planet formation and composition), and exploring the evolution of snow lines in the modeled system.