MINDS: The Very Low-mass Star and Brown Dwarf Sample Hidden Water in Carbon-dominated Protoplanetary Disks

Year: 2025

Type: article

Abstract: Infrared observations of the inner disks around very low-mass stars (VLMS; <0.3 M ⊙) have revealed a carbon-rich gas composition in the terrestrial planet-forming regions. Contrary to the typically water-rich T Tauri disk spectra, only two disks around VLMS have been observed to be water-rich among more than 10 VLMS disks observed so far with JWST/MIRI. In this Letter, we systematically search for the presence of water and other oxygen-bearing molecules in the JWST/MIRI spectra of 10 VLMS disks from the MIRI mid-INfrared Disk Survey (MINDS). In addition to the two previously reported detections of water emission in this VLMS sample, we detect water emission in the spectra of three other sources and tentatively in one source, and we provide strong evidence for water emission in the remaining disks in the MINDS sample, most of which have bright emission from carbon-bearing molecules. We show that the C2H2 emission is much stronger than that of water for sources with low luminosities, and the hydrocarbons outshine the water emission in such conditions. We propose that the appearance of water-rich versus hydrocarbon-rich spectra is related to the location of the water reservoir in the disk relative to the main hydrocarbon reservoir. Our findings indicate that the terrestrial planet-forming regions in VLMS disks have high carbon-to-oxygen ratios (C/O > 1) but can still harbor ample water, similar to those in the T Tauri disks.

Source: The Astrophysical Journal Letters

DOI: 10.3847/2041-8213/adc692

Institutions: University of Groningen, Leiden University, Max Planck Institute for Extraterrestrial Physics, Leiden Observatory, Max Planck Institute for Astronomy, Radboud University Nijmegen, University of Liège, KU Leuven, University of Arizona, Carnegie Institution for Science, Earth and Planets Laboratory, Centro de Astrobiología, University of Vienna, ETH Zurich, Institute for Particle Physics and Astrophysics, Centre National de la Recherche Scientifique, Université Paris Cité, Commissariat à l'Énergie Atomique et aux Énergies Alternatives, Université Paris-Saclay, Astrophysique, Instrumentation et Modélisation, CEA Paris-Saclay, Dublin Institute For Advanced Studies, Astronomical Observatory of Capodimonte, National Institute for Astrophysics, Space Research Organisation Netherlands, Austrian Academy of Sciences, University of Exeter, Graz University of Technology, Space Research Institute, Institut d'Astrophysique Spatiale

Language: English

Topic: Astrophysics and Star Formation Studies

Subfield: Astronomy and Astrophysics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $2,400

Funders: National Aeronautics and Space Administration, Space Telescope Science Institute, European Space Agency, National Research Foundation, Enterprise Ireland, Danmarks Grundforskningsfond, Swedish National Space Agency, Fonds De La Recherche Scientifique - FNRS, Belgian Federal Science Policy Office, Centre National d’Etudes Spatiales, Nederlandse Organisatie voor Wetenschappelijk Onderzoek, Nuclear Safety and Security Commission, Max-Planck-Gesellschaft, Centre National de la Recherche Scientifique, Horizon 2020 Framework Programme, Science and Technology Facilities Council, Agencia Estatal de Investigación, H2020 European Research Council

OpenAlex ID: W4410138125