SPHEREx Widefield Infrared Spectral Mapping of Interstellar Ices and Polycyclic Aromatic Hydrocarbons

Abstract We present some of the first infrared spectral maps acquired by SPHEREx. These maps, which to our knowledge are the largest of their type ever compiled in the near-infrared, reveal multiple strong lines due to interstellar ices and polycyclic aromatic hydrocarbons (PAHs) throughout the Cygnus X and North American Nebula regions. The maps emphasize the strongest features arising from the 3 μ m H 2 O, 4.27 μ m CO 2 , and 4.67 μ m CO lines and the 3.28 μ m PAH feature, all of which are detected over large areas with complex and filamentary spatial distributions. The ice absorption maps of H 2 O and CO 2 in particular broadly trace dense, cold, and well-shielded regions across Cygnus X, consistent with the established picture of efficient ice formation in dense molecular clouds. The interstellar ice features are also detected abundantly in diffuse absorption over wide areas. The relative strengths of the H 2 O and CO 2 features vary among different lines of sight, indicating possible differences in local physical conditions or chemical variations. The 3.28 μ m PAH emission correlates with the emission from the 7.7 and 11.2 μ m features but shows small differences that may trace the grain-size distribution and variations in the ambient UV field. SPHEREx all-sky spectral imaging—only a small fraction of which is showcased in this work—will support numerous science investigations, including the structure of the Galaxy, the physics of the interstellar medium, and the chemistry of stars.

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Publication Details

Journal
The Astrophysical Journal
Published
2026-04-15
DOI
https://doi.org/10.3847/1538-4357/ae5180
Primary Topic
Astrophysics and Star Formation Studies
Type
article
Field-Weighted Citation Impact
0.00

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article

SPHEREx Widefield Infrared Spectral Mapping of Interstellar Ices and Polycyclic Aromatic Hydrocarbons

Yi-Kuan Chiang, Volker Tolls, Tzu‐Ching Chang, Gary J. Melnick et al.
The Astrophysical Journal
Astrophysics and Star Formation Studies
article

SPHEREx Widefield Infrared Spectral Mapping of Interstellar Ices and Polycyclic Aromatic Hydrocarbons

Yi-Kuan Chiang, Volker Tolls, Tzu‐Ching Chang, Gary J. Melnick, R. Paladini, Joseph L. Hora, Yujin Yang, Olivier Doré, Ji Yeon Seok, S Bruton, Phil Korngut, B. P. Crill, Woong-Seob Jeong, Zhaoyu Huai, Shuang-Shuang Chen, Miju Kang, H. Hui, Daniel Masters, M. W. Werner, J. J. Bock, J S Kim, Andreas L. Faisst, Robin Y. Wen, Giulia Murgia, J. W. Noh, Matthew L. N. Ashby, Ari J. Cukierman, Zafar Rustamkulov, Michael Zemcov, Brandon S. Hensley, Carey M. Lisse, Jeong-Eun Lee, Asantha Cooray
article en

Abstract

Abstract We present some of the first infrared spectral maps acquired by SPHEREx. These maps, which to our knowledge are the largest of their type ever compiled in the near-infrared, reveal multiple strong lines due to interstellar ices and polycyclic aromatic hydrocarbons (PAHs) throughout the Cygnus X and North American Nebula regions. The maps emphasize the strongest features arising from the 3 μ m H 2 O, 4.27 μ m CO 2 , and 4.67 μ m CO lines and the 3.28 μ m PAH feature, all of which are detected over large areas with complex and filamentary spatial distributions. The ice absorption maps of H 2 O and CO 2 in particular broadly trace dense, cold, and well-shielded regions across Cygnus X, consistent with the established picture of efficient ice formation in dense molecular clouds. The interstellar ice features are also detected abundantly in diffuse absorption over wide areas. The relative strengths of the H 2 O and CO 2 features vary among different lines of sight, indicating possible differences in local physical conditions or chemical variations. The 3.28 μ m PAH emission correlates with the emission from the 7.7 and 11.2 μ m features but shows small differences that may trace the grain-size distribution and variations in the ambient UV field. SPHEREx all-sky spectral imaging—only a small fraction of which is showcased in this work—will support numerous science investigations, including the structure of the Galaxy, the physics of the interstellar medium, and the chemistry of stars.

The Astrophysical JournalVol. 1001(2)
California Institute of Technology (US), Institute of Astronomy and Astrophysics, Academia Sinica (TW), Jet Propulsion Laboratory (US), Seoul National University (KR), Johns Hopkins University (US), Rochester Institute of Technology (US), University of California, Irvine (US), Korea Astronomy and Space Science Institute (KR), Johns Hopkins University Applied Physics Laboratory (US), Center for Astrophysics Harvard & Smithsonian (US)
National Aeronautics and Space Administration, National Research Foundation of Korea
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Astrophysics and Star Formation Studies
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