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JWST/NIRCam detections of dusty subsolar-mass young stellar objects in the Small Magellanic Cloud

Nature Astronomy volume 7, pages 694–701 (2023)Cite this article

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Abstract

Low-mass stars are the most numerous stellar objects in the Universe. Before the James Webb Space Telescope (JWST), we had limited knowledge of how planetary systems around low-mass stars could form at subsolar metallicities. Here we present JWST observations of NGC 346, a star-forming region in the metal-poor Small Magellanic Cloud, revealing a substantial population of subsolar-mass young stellar objects (YSOs) with an infrared excess. We notice that continuing low-mass star formation is concentrated along dust filaments. We detected roughly 500 YSOs and pre-main-sequence (PMS) stars from more than 45,000 unique sources, using all four NIRCam wide filters with deep, high-resolution imaging. From these observations, we construct detailed near-infrared colour–magnitude diagrams with which preliminary categorizations of YSO classes are made. For the youngest, most deeply embedded objects, JWST/NIRCam is ten magnitudes more sensitive than Spitzer observations at comparable wavelengths, and reaches two magnitudes fainter than Hubble Space Telescope for more evolved PMS sources, corresponding to roughly 0.1 M⊙. The infrared sensitivity and resolution of JWST allows us to detect embedded low-mass star formation in an extragalactic environment. Furthermore, evidence of infrared excesses and accretion suggests that the dust required for rocky planet formation is present at metallicities as low as 0.2 Z⊙, which are akin to those in place at cosmic noon.

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Fig. 1: NIRCam mosaics of NGC 346.
Fig. 2: CMDs and colour–colour diagrams highlighting sources classified photometrically and as stellar density Hess diagrams for all point sources in the NGC 346 catalogue.

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Data availability

The data used in this study may be obtained from the Mikulski Archive for Space Telescopes (MAST, https://mast.stsci.edu/) and are associated with program no. 1227.

Code availability

This research made use of astropy56, photutils53 and topcat57. The starbug II tool52 optimized for JWST–NIRCam and MIRI point-source photometry in complex crowded environments is available via pip install starbug2.

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Acknowledgements

This work is based on observations made with the NASA/ESA/CSA JWST. 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 no. NAS 5-03127 for JWST. These observations are associated with program no. 1227. O.C.J. acknowledges support from a Science and Technology Facilities Council Webb fellowship. K.F. acknowledges support through the ESA Research Fellowship. M.M. acknowledges support through a NASA/JWST grant no. 80NSSC22K0025. M.M., N.H. and L.L. acknowledge support from the National Science Foundation through grant no. 2054178. L.E.U.C. was supported by an appointment to the NASA Postdoctoral Program at the NASA Ames Research Center, administered by Oak Ridge Associated Universities under contract with NASA. O.N. acknowledges support from STScI Director’s Discretionary Fund.

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Authors and Affiliations

  1. UK Astronomy Technology Centre, Royal Observatory, Edinburgh, UK

    Olivia C. Jones

  2. Institute for Astronomy, University of Edinburgh, Edinburgh, UK

    Conor Nally

  3. Stratospheric Observatory for Infrared Astronomy, NASA Ames Research Center, Moffett Field, CA, USA

    Nolan Habel, Laura Lenkić & Margaret Meixner

  4. European Space Research and Technology Centre, European Space Agency, Noordwijk, the Netherlands

    Katja Fahrion, Guido De Marchi & Giovanna Giardino

  5. Space Telescope Science Institute, Baltimore, MD, USA

    Alec S. Hirschauer, Omnarayani Nayak, Massimo Robberto, Elena Sabbi, Tracy Beck, Charles Keyes, James Muzerolle, Nino Panagia, Klaus Pontoppidan, B. A. Sargent & David Soderblom

  6. NASA Postdoctoral Program Fellow, NASA Ames Research Center, Moffett Field, CA, USA

    Laurie E. U. Chu

  7. Johns Hopkins University, Baltimore, MD, USA

    Massimo Robberto & B. A. Sargent

  8. AURA for the European Space Agency, Space Telescope Science Institute, Baltimore, MD, USA

    Peter Zeidler

  9. ESAC, European Space Agency (ESA), Madrid, Spain

    Catarina Alves de Oliveira

  10. INAF, Astronomical Observatory of Rome, Monteporzio Catone, Italy

    Katia Biazzo

  11. Leiden Observatory, Leiden University, Leiden, the Netherlands

    Bernhard Brandl & Ciaran Rogers

  12. European Southern Observatory, Garching, Germany

    Teresa Jerabkova

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Contributions

O.C.J. led the analysis and is the science lead of the NGC 346 Team. C.N. produced the photometric catalogues. N.H. and L.L. reprocessed the NIRCam data. K.F. and C.R. assisted in the photometry. M.R., G.d.M. and E.S. provided advice on NIRCam data processing and the analysis on comparison to HST data. L.E.U.C. produced images on NGC 346. A.S.H., M.M. and K.P. helped optimize the observations. All authors contributed to observation planning and/or scientific interpretation.

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Correspondence to Olivia C. Jones.

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Jones, O.C., Nally, C., Habel, N. et al. JWST/NIRCam detections of dusty subsolar-mass young stellar objects in the Small Magellanic Cloud. Nat Astron 7, 694–701 (2023). https://doi.org/10.1038/s41550-023-01945-7

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