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Published April 10, 2026 | Version Published
Journal Article Open

A JWST MIRI LRS Survey of 37 Massive Star-forming Galaxies and Active Galactic Nuclei at Cosmic Noon: Overview and First Results

Creators

  • 1. ROR icon The University of Texas at Austin
  • 2. NASA Hubble Fellow.
  • 3. ROR icon University of Massachusetts Amherst
  • 4. ROR icon Tufts University
  • 5. ROR icon Space Telescope Science Institute
  • 6. ROR icon University of Arizona
  • 7. ROR icon University of Kansas
  • 8. ROR icon Infrared Processing and Analysis Center
  • 9. ROR icon University of California, Santa Barbara
  • 10. ROR icon FORTH Institute of Astrophysics
  • 11. ROR icon European University Cyprus
  • 12. ROR icon Goddard Space Flight Center
  • 13. ROR icon University of Washington
  • 14. ROR icon California Institute of Technology

Abstract

We present a large spectroscopic survey with JWST’s Mid-Infrared Instrument Low Resolution Spectrometer (LRS) targeting 37 infrared-bright galaxies between z = 0.65–2.46 with infrared luminosities log L_(IR)/L⊙ > 11.5 and log M*/M⊙ = 10 − 11.5. Targets were taken from a Spitzer 24 μm selected sample with archival spectroscopy from the Infrared Spectrograph (IRS) and include a mix of star-forming galaxies and dust-obscured active galactic nuclei. By combining IRS with the increased sensitivity of LRS, we expand the range of spectral features observed between 5 and 30 μm for every galaxy in our sample. In this paper, we outline the sample selection, reduction of the JWST data, extraction of the 1D spectra, and polycyclic aromatic hydrocarbon (PAH) feature measurements from λrest = 3.3–11.3 μm. In the JWST spectra, we detect PAH emission features at 3.3–5.3 μm, as well as Paschen and Brackett lines. The 3.3 μm feature can be as bright as 1% of the 8–1000 μm infrared luminosity and exhibits a tight correlation with the dust-obscured star formation rate. We detect absorption features from CO gas, CO2 ice, H2O ice, and aliphatic dust. From the joint JWST and Spitzer analysis, we find that the 11.3/3.3 μm PAH ratios are on average three times higher than that of local luminous infrared galaxies. This is interpreted as evidence that the PAH grains are larger at z ∼ 1–2. The size distribution may be affected by coagulation of grains due to high gas densities and low temperatures. These conditions are supported by the observation of strong water ice absorption at 3.05 μm and can lower stellar radiative feedback because large PAHs transmit less energy per photon into the interstellar medium.

Copyright and License

© 2026. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.

Acknowledgement

J.M. acknowledges S. Kendrew and the whole MIRI Instrument Science team who supported this project. J.M. acknowledges the invaluable labor of the maintenance and clerical staff at our institutions, whose contributions make our scientific discoveries a reality. Authors from UT Austin acknowledge that UT is an institution that sits on indigenous land. The Tonkawa lived in central Texas, and the Comanche and Apache moved through this area. We pay our respects to all the American Indian and Indigenous Peoples and communities who have been or have become a part of these lands and territories in Texas. We are grateful to be able to live, work, collaborate, and learn on this piece of Turtle Island.

J.M. thanks NASA and acknowledges support through the Hubble Fellowship Program, awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS 5-26555. This work is based [in part] on observations made with the NASA/ESA/CSA James Webb Space Telescope. 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 NAS 5-03127 for JWST. These observations are associated with program #3224. Support for program #3224 was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-03127.

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Additional details

Related works

Is supplemented by
Dataset: 10.17909/18v0-8068 (DOI)

Funding

National Aeronautics and Space Administration
NAS 5-26555
National Aeronautics and Space Administration
NAS 5-03127
Space Telescope Science Institute

Dates

Submitted
2025-10-08
Accepted
2026-03-02
Available
2026-04-07
Published

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Caltech groups
Infrared Processing and Analysis Center (IPAC) , Division of Physics, Mathematics and Astronomy (PMA)
Publication Status
Published