MINDS: The Very Low-mass Star And Brown Dwarf Sample — Hidden Water In Carbon-dominated Protoplanetary Disks

Infrared observations of the inner disks around very low-mass stars (VLMS, <0.3M_⊙) 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 ten 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 ten 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 vs. 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.

Aditya M. Arabhavi (1), Inga Kamp (1), Ewine F. van Dishoeck (2 and 3), Thomas Henning (4), Hyerin Jang (5), Valentin Christiaens (6 and 7), Danny Gasman (6), Ilaria Pascucci (8), Giulia Perotti (4), Sierra L. Grant (9), David Barrado (10), Manuel Güdel (11 and 12), Pierre-Olivier Lagage (13), Alessio Caratti o Garatti (14 and 15), Fred Lahuis (16), L. B. F. M. Waters (5 and 17), Till Kaeufer (18 and 1 and 17 and 19 and 20), Jayatee Kanwar (1 and 18 and 21), Maria Morales-Calderón (10), Kamber Schwarz (4), Andrew D. Sellek (2), Benoît Tabone (22), Milou Temmink (2), Marissa Vlasblom (2) ((1) Kapteyn Astronomical Institute, Rijksuniversiteit Groningen, Groningen, The Netherlands, (2) Leiden Observatory, Leiden University, Leiden, the Netherlands, (3) Max-Planck Institut für Extraterrestrische Physik (MPE), Garching, Germany, (4) Max-Planck-Institut für Astronomie (MPIA), Heidelberg, Germany, (5) Department of Astrophysics/IMAPP, Radboud University, Nijmegen, The Netherlands, (6) Institute of Astronomy, KU Leuven, Leuven, Belgium, (7) STAR Institute, Université de Liége, Liége, Belgium, (8) Department of Planetary Sciences, University of Arizona, Tucson, USA, (9) Earth and Planets Laboratory, Carnegie Institution for Science, Washington, USA, (10) Centro de Astrobiología (CAB), CSIC-INTA, ESAC Campus, Madrid, Spain, (11) Dept. of Astrophysics, University of Vienna, Vienna, Austria, (12) ETH Zürich, Institute for Particle Physics and Astrophysics, Zürich, Switzerland, (13) Université Paris-Saclay, Université Paris Cité, CEA, CNRS, AIM, Gif-sur-Yvette, France, (14) INAF – Osservatorio Astronomico di Capodimonte, Napoli, Italy, (15) Dublin Institute for Advanced Studies, Dublin, Ireland, (16) SRON Netherlands Institute for Space Research, Groningen, The Netherlands, (17) SRON Netherlands Institute for Space Research, Leiden, the Netherlands, (18) Space Research Institute, Austrian Academy of Sciences, Graz, Austria, (19) Institute for Theoretical Physics and Computational Physics, Graz University of Technology, Graz, Austria, (20) Department of Physics and Astronomy, University of Exeter, Exeter, UK, (21) TU Graz, Fakultät für Mathematik, Physik und Geodäsie, Graz, Austria, (22) Université Paris-Saclay, CNRS, Institut d’Astrophysique Spatiale, Orsay, France)

Comments: Accepted for publication in Astrophysical Journal Letters, 21 pages, 24 figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:2504.11425 [astro-ph.EP] (or arXiv:2504.11425v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2504.11425
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Submission history
From: Aditya Mahadeva Arabhavi
[v1] Tue, 15 Apr 2025 17:38:14 UTC (8,573 KB)
https://arxiv.org/abs/2504.11425
Astrobiology,