The Effect of Dust Evolution and Traps on Inner Disk Water Enrichment

TL;DR

This study investigates how dust traps and gaps in protoplanetary disks influence water vapor enrichment in the inner regions, highlighting the roles of turbulence, fragmentation velocity, and disk substructures in volatile delivery.

Contribution

It introduces a volatile-inclusive multi-Myr disk evolution model that accounts for dust traps and gaps, revealing their impact on inner disk water enrichment, a novel aspect in disk evolution studies.

Findings

Inner disk vapor enrichment is sensitive to turbulence and fragmentation velocity.

Shallow inner gaps can leak material, affecting water delivery.

Gaps play a more crucial role than planetesimal formation in volatile regulation.

Abstract

Substructures in protoplanetary disks can act as dust traps that shape the radial distribution of pebbles. By blocking the passage of pebbles, the presence of gaps in disks may have a profound effect on pebble delivery into the inner disk, crucial for the formation of inner planets via pebble accretion. This process can also affect the delivery of volatiles (such as H$_2$O) and their abundance within the water snow line region (within a few au). In this study, we aim to understand what effect the presence of gaps in the outer gas disk may have on water vapor enrichment in the inner disk. Building on previous work, we employ a volatile-inclusive multi-Myr disk evolution model that considers an evolving ice-bearing drifting dust population, sensitive to dust-traps, which loses its icy content to sublimation upon reaching the snow line. We find that vapor abundance in the inner disk is strongly affected by fragmentation velocity (v$_{\rm f}$) and turbulence, which control how intense vapor enrichment from pebble delivery is, if present, and how long it may last. Generally, for disks with low to moderate turbulence ($\alpha$ $\le$ 1 $\times$ 10$^{-3}$) and for a range of v$_{\rm f}$, radial location, and gap depth (especially that of the innermost gaps), can significantly alter enrichment. Shallow inner gaps may continuously leak material from beyond it, despite the presence of additional deep outer gaps. We finally find that the for realistic v$_{\rm f}$ ($\le$ 10 m s$^{-1}$), presence of gaps is more important than planetesimal formation beyond the snow line in regulating pebble and volatile delivery into the inner disk.