Year: 2026
Type: article
Abstract: Pebble drift is an important mechanism for supplying the materials needed to build planets in the inner region of protoplanetary disks. Thus, constraining pebble drift’s timescales and mass flux is essential to understanding planet formation history. Current pebble drift models suggest pebble fluxes can be constrained from the enhancement of gaseous volatile abundances when icy pebbles sublimate after drifting across key snowlines. In this work, we present Atacama Large Millimeter/submillimeter Array observations of spatially resolved 13 C 18 O J = 2–1 line emission inside the midplane CO snowline of the HD 163296 and MWC 480 protoplanetary disks. We use radiative transfer and thermochemical models to constrain the spatial distribution of CO gas column density. We find that both disks display centrally peaked CO abundance enhancement of up to 10 times of the Interstellar Medium (ISM) abundance levels. For HD 163296 and MWC 480, the inferred enhancements require 250–350 and 480–660 M ⊕ of pebbles to have drifted across their CO snowlines, respectively. These ranges fall within cumulative pebble mass flux ranges to grow gas giants in the interior to the CO snowline. The centrally peaked CO enhancement is unexpected in current pebble drift models, which predict CO enhancement peaks at the CO snowline, or is uniform inside the snowline. We propose two hypotheses to explain the centrally peaked CO enhancement, including a large CO desorption distance and CO trapped in water ice. By testing both hypotheses with the 1D gas and dust evolution code chemcomp , we find that volatile trapping (about 30%) best reproduces the centrally peaked CO enhancement observed.
Source: The Astrophysical Journal
Institutions: University of Wisconsin–Madison, University of Exeter, University of Leeds, Massachusetts Institute of Technology, University of Virginia, Boston University, Center for Astrophysics Harvard & Smithsonian, University of Michigan, Institut de Radioastronomie Millimétrique, Institut de Planétologie et d'Astrophysique de Grenoble, Université Grenoble Alpes, University of Arizona, Columbia University, University of Florida, University of Milan
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $4,499
Funders: National Science Foundation, National Aeronautics and Space Administration, Space Telescope Science Institute, National Radio Astronomy Observatory, European Commission, Korea Astronomy and Space Science Institute, National Astronomical Observatory of Japan, Science and Technology Facilities Council, National Institutes of Natural Sciences
OpenAlex ID: W7130333300