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Published February 20, 2026 | Version Published
Journal Article Open

Protoplanetary Disk Cavities with JWST-MIRI: A Dichotomy in Molecular Emission

Creators

  • 1. ROR icon Texas State University
  • 2. ROR icon Vassar College
  • 3. ROR icon University of Arizona
  • 4. ROR icon University College London
  • 5. ROR icon NOIRLab
  • 6. ROR icon Jet Propulsion Lab
  • 7. ROR icon University of Exeter
  • 8. ROR icon California Institute of Technology
  • 9. ROR icon Institut d'Astrophysique Spatiale
  • 10. ROR icon University of Wisconsin–Madison
  • 11. ROR icon Columbia University
  • 12. ROR icon University of Milan
  • 13. ROR icon Harvard-Smithsonian Center for Astrophysics
  • 14. ROR icon University of Michigan–Ann Arbor
  • 15. ROR icon Diego Portales University
  • 16. ROR icon University of Virginia
  • 17. ROR icon European Southern Observatory
  • 18. ROR icon Space Science Institute

Abstract

The evolution of planet-forming regions in protoplanetary disks is of fundamental importance to understanding planet formation. Disks with a central deficit in dust emission, a “cavity,” have long attracted interest as potential evidence for advanced disk clearing by protoplanets and/or winds. Before JWST, infrared spectra showed that these disks typically lack the strong molecular emission observed in full disks. In this work, we combine a sample of 12 disks with millimeter cavities of a range of sizes (∼2–70 au) and different levels of millimeter and infrared continuum deficits. We analyze their molecular spectra as observed with MIRI on JWST, homogeneously reduced with the new JDISCS pipeline. This analysis demonstrates a stark dichotomy in molecular emission where “molecule-rich” (MR) cavities follow global trends between water, CO, and OH luminosity and accretion luminosity as in full disks, while “molecule-poor” (MP) cavities are significantly subluminous in all molecules except sometimes OH. Disk cavities generally show subluminous organic emission, higher OH/H2O ratios, and suggest a lower water column density. The subthermal excitation of CO and water vibrational lines suggests a decreased gas density in the emitting layer in all cavities, supporting model expectations for C2H2 photodissociation. We discover a bifurcation in the infrared index (lower in MR cavities) suggesting that the molecular dichotomy is linked to residual μm-size dust within millimeter disk cavities. Put together, these results suggest a feedback process between dust depletion, gas density decrease, and molecule dissociation. Disk cavities may have a common evolutionary sequence where MR switch into MP over time.

Copyright and License

© 2026. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.

Acknowledgement

The authors acknowledge feedback from an anonymous referee who helped significantly improve the discussion of organics, as well as helpful discussions on the topic with Jayatee Kanwar. The authors are thankful to Marissa Vlasblom for providing new model line fluxes for comparison to the data in Figure 18, and to Joshua Sendgikoski for help with stellar age estimates. This work is based on observations made with the NASA/ ESA/CSA James Webb Space Telescope. The JWST data used in this paper were obtained from the Mikulski Archive for Space Telescopes (MAST) at the Space Telescope Science Institute and can be accessed via: doi: 10.17909/4gpn-y657. The data were obtained from the Mikulski Archive for Space Telescopes at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-03127 for JWST. The observations are associated with JWST GO Cycle 1 and 2 programs 1282, 1549, 1584, 1640, 2025, 2260, 3228.

Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (80NM0018D0004). The authors acknowledge support from NASA/Space Telescope Science Institute grants: JWST-GO-01640 and JWST-GO-01584. S.K. and T.K. acknowledge support from STFC grant ST/Y002415/1. B.T. acknowledges support by the Programme National PCMI of CNRS/INSU with INC/INP cofunded by CEA and CNES.

Facilities

JWST - James Webb Space Telescope.

Software References

Matplotlib (J. D. Hunter 2007), NumPy (S. van der Walt et al. 2011), SciPy (P. Virtanen et al. 2020), Seaborn (M. Waskom 2021), Astropy (Astropy Collaboration et al. 2013, 2018, 2022), LMFIT (M. Newville et al. 2014), iSLAT (E. G. Jellison et al. 2024; M. Johnson et al. 2024).

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Additional details

Related works

Is new version of
Discussion Paper: arXiv:2601.02344 (arXiv)
Is supplemented by
Dataset: 10.17909/4gpn-y657 (DOI)

Funding

National Aeronautics and Space Administration
NAS 5-03127
National Aeronautics and Space Administration
80NM0018D0004
Space Telescope Science Institute
JWST-GO-01640
Space Telescope Science Institute
JWST-GO-01584
Science and Technology Facilities Council
ST/Y002415/1
Centre National de la Recherche Scientifique
Institut National des Sciences de l'Univers

Dates

Submitted
2025-08-27
Accepted
2025-12-30
Available
2026-02-13
Published

Caltech Custom Metadata

Caltech groups
Division of Geological and Planetary Sciences (GPS)
Publication Status
Published