MINDS: The very low-mass star and brown dwarf sample
Astronomy and Astrophysics, vol. 699, pp. A194
Abstract
Context . 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 2 H 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. Aims . 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). Methods . 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. Results . 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 2 H 2 and HCN in all the sources and find larger hydrocarbons, such as C 4 H 2 and C 6 H 6 , in nearly all sources. Among oxygen-bearing molecules, we find firm detections of CO 2 , H 2 O, 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.
Authors 23
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Affiliation as printed
Kapteyn Astronomical Institute, Rijksuniversiteit Groningen, Postbus 800, 9700AV Groningen, The Netherlands
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Affiliation as printed
Kapteyn Astronomical Institute, Rijksuniversiteit Groningen, Postbus 800, 9700AV Groningen, The Netherlands
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Max Planck Institute for Astronomy
Affiliation as printed
Max-Planck-Institut für Astronomie (MPIA), Königstuhl 17, 69117 Heidelberg, Germany
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Leiden University · Max Planck Institute for Extraterrestrial Physics · Leiden Observatory
Affiliation as printed
Leiden Observatory, Leiden University, 2300 RA Leiden, The Netherlands
Max-Planck Institut für Extraterrestrische Physik (MPE), Giessenbachstr. 1, 85748 Garching, Germany
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Affiliation as printed
Department of Astrophysics/IMAPP, Radboud University, PO Box 9010, 6500 GL Nijmegen, The Netherlands
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Radboud University Nijmegen · Space Research Organisation Netherlands
Affiliation as printed
Department of Astrophysics/IMAPP, Radboud University, PO Box 9010, 6500 GL Nijmegen, The Netherlands
SRON Netherlands Institute for Space Research, Niels Bohrweg 4, 2333 CA Leiden, The Netherlands
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University of Liège · KU Leuven
Affiliation as printed
Institute of Astronomy, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
STAR Institute, Université de Liège, Allée du Six Août 19c, 4000 Liège, Belgium
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Affiliation as printed
Institute of Astronomy, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
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Affiliation as printed
1629 East University Boulevard, Tucson, AZ 85721, USA
Department of Planetary Sciences, University of Arizona
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University of Copenhagen · Max Planck Institute for Astronomy
Affiliation as printed
Max-Planck-Institut für Astronomie (MPIA), Königstuhl 17, 69117 Heidelberg, Germany
Niels Bohr Institute, University of Copenhagen, NBB BA2, Jagtvej 155A, 2200 Copenhagen, Denmark
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University of Vienna · ETH Zurich · Institute for Particle Physics and Astrophysics
Affiliation as printed
Dept. of Astrophysics, University of Vienna, Türkenschanzstr. 17, 1180 Vienna, Austria
ETH Zürich, Institute for Particle Physics and Astrophysics, Wolfgang-Pauli-Str. 27, 8093 Zürich, Switzerland
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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
Affiliation as printed
Université Paris-Saclay, Université Paris Cité, CEA, CNRS, AIM, 91191 Gif-sur-Yvette, France
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Affiliation as printed
Centro de Astrobiología (CAB), CSIC-INTA, ESAC Campus, Camino Bajo del Castillo s/n, 28692 Villanueva de la Cañada, Madrid, Spain
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Astronomical Observatory of Capodimonte
Affiliation as printed
INAF – Osservatorio Astronomico di Capodimonte, Salita Moiariello 16, 80131 Napoli, Italy
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Space Research Organisation Netherlands
Affiliation as printed
SRON Netherlands Institute for Space Research, PO Box 800, 9700 AV, Groningen, The Netherlands
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Affiliation as printed
Department of Physics and Astronomy, University of Exeter, Exeter EX4 4QL, UK
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Affiliation as printed
Centro de Astrobiología (CAB), CSIC-INTA, ESAC Campus, Camino Bajo del Castillo s/n, 28692 Villanueva de la Cañada, Madrid, Spain
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Max Planck Institute for Astronomy
Affiliation as printed
Max-Planck-Institut für Astronomie (MPIA), Königstuhl 17, 69117 Heidelberg, Germany
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Leiden University · Leiden Observatory
Affiliation as printed
Leiden Observatory, Leiden University, 2300 RA Leiden, The Netherlands
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Centre National de la Recherche Scientifique · Université Paris-Saclay · Institut d'Astrophysique Spatiale
Affiliation as printed
Université Paris-Saclay, CNRS, Institut d'Astrophysique Spatiale, 91405 Orsay, France
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Leiden University · Leiden Observatory
Affiliation as printed
Leiden Observatory, Leiden University, 2300 RA Leiden, The Netherlands
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Leiden University · Leiden Observatory
Affiliation as printed
Leiden Observatory, Leiden University, 2300 RA Leiden, The Netherlands
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ETH Zurich · Institute for Particle Physics and Astrophysics
Affiliation as printed
ETH Zürich, Institute for Particle Physics and Astrophysics, Wolfgang-Pauli-Str. 27, 8093 Zürich, Switzerland
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