MINDS: The very low-mass star and brown dwarf sample. Detections and trends in the inner disk gas

Planet-forming disks around brown dwarfs and very low-mass stars (VLMS) are, on average, less massive and are expected to undergo faster radial solid transport than their higher-mass counterparts. Spitzer had detected C_2H_2 CO_2 and HCN around these objects but did not provide a firm detection of water. With a better sensitivity and spectral resolving power than that of Spitzer the James Webb Space Telescope (JWST) has recently revealed incredibly carbon-rich spectra and only one water-rich spectrum from such disks. A study of a larger sample of objects is necessary to understand how common such carbon-rich inner disk regions are and to put constraints on their evolution. We present and analyze JWST MIRI/MRS observations of ten disks around VLMS from the MIRI guaranteed time observations program. This sample is diverse, with the central object ranging in mass from 0.02 to 0.14 M_⊙. They are located in three star-forming regions and a moving group (1 to 10,Myr). We identified molecular emission in all sources based on recent literature and spectral inspection, and reported detection rates. We compared the molecular flux ratios between different species and to dust emission strengths. We also compared the flux ratios with the stellar and disk properties. The spectra of these VLMS disks are extremely rich in molecular emission, and we detect the 10,μm silicate dust emission feature in 70% of the sample. We detect C_2H_2 and HCN in all the sources and find larger hydrocarbons, such as C_4H_2 and C_6H_6 in nearly all sources. Among oxygen-bearing molecules, we find firm detections of CO_2 H_2O and CO in 90%, 50%, and 20% of the sample, respectively. We find that the detection rates of organic molecules correlate with other organic molecules and anticorrelate with the detection rates of inorganic molecules. Hydrocarbon-rich sources show weaker 10,μm dust strengths, as well as lower disk dust masses (measured from millimeter fluxes) than the oxygen-rich sources. We find evidence for a C/O ratio enhancement with disk age. The observed trends are consistent with models that suggest rapid inward solid material transport and grain growth.

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Publication Details

Journal
Astronomy and Astrophysics
Published
2025-06-11
DOI
https://doi.org/10.1051/0004-6361/202554109
Citations
15
Primary Topic
Spectroscopy and Laser Applications
Type
article
Field-Weighted Citation Impact
11.34

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article

MINDS: The very low-mass star and brown dwarf sample. Detections and trends in the inner disk gas

Hyerin Jang, M. G"udel, F. Lahuis, I. Kamp et al.
15 citations
Astronomy and Astrophysics
Spectroscopy and Laser Applications
11.34
article

MINDS: The very low-mass star and brown dwarf sample. Detections and trends in the inner disk gas

Hyerin Jang, M. G"udel, F. Lahuis, I. Kamp, Milou Temmink, J. S. Kanwar, Marissa Vlasblom, A. Caratti o Garatti, Aditya M. Arabhavi, Kamber R. Schwarz, Andrew D. Sellek, Valentin Christiaens, D. Barrado, Benoît Tabone, M. Morales‐Calderón, Giulia Perotti, Polychronis Patapis, Till Kaeufer, Danny Gasman, I. Pascucci, Steven L. Grant, L. B. F. M. Waters, P. O. Lagage, Th. Henning, E. F. van Dishoeck
article en
15 citations

Abstract

Planet-forming disks around brown dwarfs and very low-mass stars (VLMS) are, on average, less massive and are expected to undergo faster radial solid transport than their higher-mass counterparts. Spitzer had detected C_2H_2 CO_2 and HCN around these objects but did not provide a firm detection of water. With a better sensitivity and spectral resolving power than that of Spitzer the James Webb Space Telescope (JWST) has recently revealed incredibly carbon-rich spectra and only one water-rich spectrum from such disks. A study of a larger sample of objects is necessary to understand how common such carbon-rich inner disk regions are and to put constraints on their evolution. We present and analyze JWST MIRI/MRS observations of ten disks around VLMS from the MIRI guaranteed time observations program. This sample is diverse, with the central object ranging in mass from 0.02 to 0.14 M_⊙. They are located in three star-forming regions and a moving group (1 to 10,Myr). We identified molecular emission in all sources based on recent literature and spectral inspection, and reported detection rates. We compared the molecular flux ratios between different species and to dust emission strengths. We also compared the flux ratios with the stellar and disk properties. The spectra of these VLMS disks are extremely rich in molecular emission, and we detect the 10,μm silicate dust emission feature in 70% of the sample. We detect C_2H_2 and HCN in all the sources and find larger hydrocarbons, such as C_4H_2 and C_6H_6 in nearly all sources. Among oxygen-bearing molecules, we find firm detections of CO_2 H_2O and CO in 90%, 50%, and 20% of the sample, respectively. We find that the detection rates of organic molecules correlate with other organic molecules and anticorrelate with the detection rates of inorganic molecules. Hydrocarbon-rich sources show weaker 10,μm dust strengths, as well as lower disk dust masses (measured from millimeter fluxes) than the oxygen-rich sources. We find evidence for a C/O ratio enhancement with disk age. The observed trends are consistent with models that suggest rapid inward solid material transport and grain growth.

Astronomy and Astrophysics
Leiden University (NL), Centre National de la Recherche Scientifique (FR), University of Vienna (AT), University of Arizona (US), Austrian Academy of Sciences (AT), Radboud University Nijmegen (NL), University of Liège (BE), University of Groningen (NL), Carnegie Institution for Science (US), Université Paris Cité (FR), University of Exeter (GB), Commissariat à l'Énergie Atomique et aux Énergies Alternatives (FR), Université Paris-Saclay (FR), Astronomical Observatory of Capodimonte (IT), ETH Zurich (CH), Astrophysique, Instrumentation et Modélisation (FR), Space Research Institute (AT), Max Planck Institute for Extraterrestrial Physics (DE), Institut d'Astrophysique Spatiale (FR), Max Planck Institute for Astronomy (DE), Institute of Astronomy (RU), CEA Paris-Saclay (FR), Centro de Astrobiología (ES), Space Research Organisation Netherlands (NL), KU Leuven (BE)
National Aeronautics and Space Administration, Space Telescope Science Institute, Enterprise Ireland, Belgian Federal Science Policy Office, Centre National d’Etudes Spatiales, Nederlandse Organisatie voor Wetenschappelijk Onderzoek, Science and Technology Facilities Council
Openalex Percentile: Top 1%
Spectroscopy and Laser Applications
11.34
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