Radial Drift of Dust in Protoplanetary Disks: The Evolution of Ice lines and Dead zones

TL;DR

This paper presents a new model for the evolution of dust and ice lines in protoplanetary disks, highlighting their impact on dead zones and planet formation, with implications supported by recent ALMA observations.

Contribution

The study introduces a coupled model of disk chemistry, temperature, and dust evolution, emphasizing the role of ice lines in shaping dust distribution and dead zone locations.

Findings

Water ice line influences maximum grain size distribution.

Dead zone edge moves inward significantly over time.

Model aligns with recent ALMA observations of disk structures.

Abstract

We have developed a new model for the astrochemical structure of a viscously evolving protoplanetary disk that couples an analytic description of the disk's temperature and density profile, chemical evolution, and an evolving dust distribution. We compute evolving radial distributions for a range of dust grain sizes, which depend on coagulation, fragmentation and radial drift processes. In particular we find that the water ice line plays an important role in shaping the radial distribution of the maximum grain size because ice coated grains are significantly less susceptible to fragmentation than their dry counterparts. This in turn has important effects on disk ionization and therefore on the location of dead zones. In comparison to a simple constant gas-to-dust ratio model for the dust as an example, we find that the new model predicts an outer dead zone edge that moves in by a factor of about 3 at 1 Myr (to 5 AU) and by a factor of about 14 by 3 Myr (to 0.5 AU). We show that the changing position of the dead zone and heat transition traps have important implications for the formation and trapping of planets in protoplanetary disks. Finally, we consider our results in light of recent ALMA observations of HL Tau and TW Hya.