JOYS: Unlocking accretion-rate diagnostics for high-mass protostars using JWST/MIRI HI lines

Astronomy and Astrophysics, vol. 709, pp. A13

Abstract

Context. While many aspects of high-mass star formation have been investigated, the accretion onto the central protostars is one of the most fundamental but less explored physical properties. The James Webb Space Telescope (JWST), through its Mid InfraRed Instrument (MIRI), offers a unique opportunity to explore tracers of accretion at less-extincted wavelengths (5–27 μm) than those studied so far, where it delivers unparalleled sensitivity and spectral resolution. Aims. We probed the capability of MIRI in its MRS/IFU mode to detect and resolve atomic Hydrogen (H I ) emission lines in such embedded objects to subsequently estimate accretion luminosities ( L acc ) and accretion rates ( Ṁ acc ) for the first time in a sample of (six) high-mass, star forming regions at different evolutionary stages. Methods. We used the dereddened H I line luminosities as tracers of accretion by applying line-to-accretion-luminosity relations ( L acc -calibrations) from the literature. As such L acc -calibrations were originally established for low-mass Class II objects, we assessed their applicability to our sample prior to estimating accretion rates. Extinction was derived from the silicate absorption feature at 9.7 μm. Results. The infrared continuum reveals, at much higher spatial resolution than before, the location of new infrared sources (protostars), towards which we detected a handful of H I lines. While a few lines are secure detections, many are tentative. The most commonly detected line is Humphreys α at 12.37 μm, followed by Humphreys β and Pfund α . Assuming that their line fluxes are dominated by accretion, we find that two of the three existing L acc -calibrations predict excessively high accretion luminosities that largely exceed their bolometric luminosities ( L bol ), and that the third L acc -calibration still overpredicts accretion luminosities for some sources. Considering the given uncertainties, estimated accretion rates are only tentative. Conclusions. This work demonstrates the great potential of JWST/MIRI to probe H I line emission that originated in the innermost regions of high-mass protostellar systems, setting the ground floor for further investigations into accretion in these objects. While this project had the ambitious goal of robustly quantifying accretion rates, we shed light on what outstanding methodological challenges remain; the most critical being the development of new L acc - calibrations for intermediate- to high-mass protostars.

Authors 17

1. S. Reyes-Reyes

   Max Planck Institute for Astronomy

   Affiliation as printed

   Max-Planck-Institut für Astronomie

2. Henrik Beuther

   Max Planck Institute for Astronomy

   Affiliation as printed

   Max-Planck-Institut für Astronomie

3. Ewine F. van Dishoeck Aachen Leiden Observatory

   Leiden University · Max Planck Society · Max Planck Institute for Extraterrestrial Physics · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University

   Max Planck Institut für Extraterrestrische Physik (MPE)

4. C. Gieser

   Max Planck Institute for Astronomy

   Affiliation as printed

   Max-Planck-Institut für Astronomie

5. A. Caratti o Garatti

   Astronomical Observatory of Capodimonte · National Institute for Astrophysics

   Affiliation as printed

   INAF–Osservatorio Astronomico di Capodimonte

6. Ł. Tychoniec Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University

7. Patrick J Kavanagh

   National University of Ireland, Maynooth

   Affiliation as printed

   Department of Physics, Maynooth University

8. Pamela Klaassen

   Royal Observatory · UK Astronomy Technology Centre

   Affiliation as printed

   UK Astronomy Technology Centre, Royal Observatory Edinburgh

9. K. Justtanont

   Chalmers University of Technology

   Affiliation as printed

   Department of Space, Earth and Environment, Chalmers University of Technology

10. Logan Francis Aachen Leiden Observatory

    Leiden University · Leiden Observatory

    Affiliation as printed

    Leiden Observatory, Leiden University

11. Valentin J. M. Le Gouellec

    Ames Research Center · Institute of Space Sciences · Consejo Superior de Investigaciones Científicas · Institut d'Estudis Espacials de Catalunya

    Affiliation as printed

    Institut de Ciencies de l’Espai (ICE-CSIC), Campus UAB

    Institut d’Estudis Espacials de Catalunya (IEEC)

    Space Science and Astrobiology Division, NASA’s Ames Research Center

12. R. Devaraj

    Dublin Institute For Advanced Studies

    Affiliation as printed

    School of Cosmic Physics, Dublin Institute for Advanced Studies

13. T. P. Ray

    Dublin Institute For Advanced Studies

    Affiliation as printed

    School of Cosmic Physics, Dublin Institute for Advanced Studies

14. Y. Q. Chen Aachen Leiden Observatory

    Leiden University · Leiden Observatory

    Affiliation as printed

    Leiden Observatory, Leiden University

15. M.G. Navarro

    Astronomical Observatory of Rome · National Institute for Astrophysics

    Affiliation as printed

    INAF-Osservatorio Astronomico di Roma

16. W.R.M. Rocha Aachen Laboratory for Astrophysics, Leiden Observatory Leiden Observatory

    Leiden University · Leiden Observatory

    Affiliation as printed

    Laboratory for Astrophysics, Leiden Observatory, Leiden University

    Leiden Observatory, Leiden University

17. M. L. van Gelder Aachen Leiden Observatory

    Leiden University · Leiden Observatory

    Affiliation as printed

    Leiden Observatory, Leiden University