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Published October 10, 2025 | Version Published
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The Potential of the SPHEREx Mission for Characterizing Polycyclic Aromatic Hydrocarbon 3.3 μm Emission in Nearby Galaxies

Creators

  • 1. ROR icon California Institute of Technology
  • 2. ROR icon Infrared Processing and Analysis Center
  • 3. ROR icon Jet Propulsion Lab
  • 4. ROR icon Hiroshima University
  • 5. ROR icon Institute of Astronomy and Astrophysics, Academia Sinica
  • 6. ROR icon Korea Astronomy and Space Science Institute
  • 7. ROR icon Harvard-Smithsonian Center for Astrophysics
  • 8. ROR icon University of California, Berkeley
  • 9. ROR icon Lawrence Berkeley National Laboratory
  • 10. ROR icon Sejong University

Abstract

Together with gas, stars, and supermassive black holes, dust is crucial in stellar and galaxy evolution. Hence, understanding galaxies’ dust properties across cosmic time is critical to studying their evolution. In addition to photometric constraints on the absorption of blue light and its reemission at infrared wavelengths, dust grain properties can be explored spectroscopically via polycyclic aromatic hydrocarbon (PAH) emission bands in the mid-IR. The new SPHEREx space telescope conducts an all-sky spectrophotometric survey of stars and galaxies at wavelengths of 0.75–5 μm, making it ideal for studying the widespread presence of the 3.3 μm PAH emission across galaxy populations out to z ∼ 0.4. In this paper, we simulated galaxy spectra to investigate SPHEREx's capability to study PAH emission in such galaxies. We find that for the all-sky survey the PAH 3.3 μm emission band flux can be measured to 30% accuracy at log (M/M⊙) > 9.5 and star formation rate (SFR) > 1 M⊙ yr⁻¹ at z = 0.1, log (M/M⊙) > 10.5 and SFR > 10 M⊙ yr⁻¹ at z = 0.2–0.3, and log (M/M⊙) > 11 and SFR > 100 M⊙ yr⁻¹ at z = 0.4. For deep SPHEREx fields, a factor of ∼10 deeper sensitivity limits can be reached. Overall, SPHEREx will enable the measurement of the 3.3 μm PAH band emission in several hundred thousand galaxies across the sky, providing a population study of the smallest dust grains (“nano grains”) and radiation properties in massive galaxies in the nearby Universe.

Copyright and License

© 2025. 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

We thank the anonymous referee for valuable input, which improved this manuscript substantially. We thank the SPHEREx science team for valuable discussions and support in writing this paper. E.Z. acknowledges the support of the Soli Deo Gloria SURF Fellow Donors. Y.K. was supported by the National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIT; No. 2021R1C1C2091550). H.I. acknowledges support from JSPS KAKENHI grant No. JP21H01129. Part of this work was done at Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (contract No. 80NM0018D0004). Based on observations collected at the European Southern Observatory under ESO programmes 179.A-2005, 198.A-2003, 1104.A-0643, 110.25A2, and 284.A-5026; on data obtained from the ESO Science Archive Facility (J. Dunlop 2016); and on data products produced by CANDIDE and the Cambridge Astronomy Survey Unit on behalf of the UltraVISTA consortium.

Facilities

AKARI - , Sloan - Sloan Digital Sky Survey Telescope, ESO:VISTA - European Southern Observatory's 4.1 meter Visible and Infrared Survey Telescope for Astronomy.

Software References

CIGALE (D. Burgarella et al. 2005; S. Noll et al. 2009; M. Boquien et al. 2019); SPHEREx Sky Simulator (B. P. Crill et al. 2020); astropy (Astropy Collaboration et al. 2013, 2018).

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Additional details

Additional titles

Alternative title
The Potential of the SPHEREx Mission for Characterizing PAH 3.3 μm Emission in Nearby Galaxies

Related works

Is new version of
Discussion Paper: arXiv:2503.21876 (arXiv)

Funding

National Research Foundation of Korea
2021R1C1C2091550
Japan Society for the Promotion of Science
JP21H01129
National Aeronautics and Space Administration
80NM0018D0004

Dates

Accepted
2025-08-18
Available
2025-10-01
Published online

Caltech Custom Metadata

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