Comparing the Near-infrared Spectral Energy Distributions from Different Stellar Population Synthesis Models with SPHEREx Observations

Abstract While stellar population synthesis (SPS) models have been widely used for spectral analysis in optical wavelengths, their characteristics remain uncertain in the near-infrared (NIR) due to a relative lack of observed NIR spectra. The spectrophotometric data from SPHEREx are well-suited for investigating the performance of SPS models in the NIR, thanks to its wide wavelength coverage over 0.75–5.0 μ m. In this work, we compare the observed SPHEREx data of SDSS compact galaxies, including 2726 non-emission-line galaxies and 1163 emission-line galaxies, to the NIR SEDs predicted from the full spectrum fitting of SDSS optical spectra. We use four different SPS models that extend into the NIR: E-MILES, Bruzual & Charlot (BC03), Charlot & Bruzual (CB19), and FSPS. We find that all four models tend to overpredict the stellar continuum at 2.4–5 μ m by 0.1–0.3 mag. This trend is particularly prominent for intermediate-age stellar populations (∼1–5 Gyr), suggesting a systematic bias in the NIR SED predictions of current SPS models. For stellar populations older than 5 Gyr, E-MILES shows relatively smaller offsets at 3.8–5 μ m compared to other models. Meanwhile, for emission-line galaxies, the SPS models underestimate the SED by up to ∼0.5 mag at longer wavelengths due to the contribution of nonstellar emission. Overall, these results highlight the necessity of refining the NIR stellar spectral features in SPS models, such as emissions from thermally pulsating asymptotic giant branch stars or molecular absorptions from cool stars.

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Journal
The Astrophysical Journal
Published
2026-11-03
DOI
https://doi.org/10.3847/1538-4357/aeb023
Primary Topic
Galaxies: Formation, Evolution, Phenomena
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article
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0.00

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article

Comparing the Near-infrared Spectral Energy Distributions from Different Stellar Population Synthesis Models with SPHEREx Observations

Tzu‐Ching Chang, Kyuseok Oh, Bomee Lee, Richard M. Feder et al.
1 links
The Astrophysical Journal
Galaxies: Formation, Evolution, Phenomena
article

Comparing the Near-infrared Spectral Energy Distributions from Different Stellar Population Synthesis Models with SPHEREx Observations

Tzu‐Ching Chang, Kyuseok Oh, Bomee Lee, Richard M. Feder, Brendan P. Crill, Zhaoyu Huai, Michael B. Zemcov, Daniel C. Masters, Andreas L. Faisst, Jeong Hwan Lee, Asantha Cooray, O. Doré, Woong-Seob Jeong, Minjin Kim, Yujin Yang, Dohyeong Kim, Howard Hui, Dohyeong Kim, Yun-Ting Cheng, Jong-Hak Woo, Chi H. Nguyen
article en

Abstract

Abstract While stellar population synthesis (SPS) models have been widely used for spectral analysis in optical wavelengths, their characteristics remain uncertain in the near-infrared (NIR) due to a relative lack of observed NIR spectra. The spectrophotometric data from SPHEREx are well-suited for investigating the performance of SPS models in the NIR, thanks to its wide wavelength coverage over 0.75–5.0 μ m. In this work, we compare the observed SPHEREx data of SDSS compact galaxies, including 2726 non-emission-line galaxies and 1163 emission-line galaxies, to the NIR SEDs predicted from the full spectrum fitting of SDSS optical spectra. We use four different SPS models that extend into the NIR: E-MILES, Bruzual & Charlot (BC03), Charlot & Bruzual (CB19), and FSPS. We find that all four models tend to overpredict the stellar continuum at 2.4–5 μ m by 0.1–0.3 mag. This trend is particularly prominent for intermediate-age stellar populations (∼1–5 Gyr), suggesting a systematic bias in the NIR SED predictions of current SPS models. For stellar populations older than 5 Gyr, E-MILES shows relatively smaller offsets at 3.8–5 μ m compared to other models. Meanwhile, for emission-line galaxies, the SPS models underestimate the SED by up to ∼0.5 mag at longer wavelengths due to the contribution of nonstellar emission. Overall, these results highlight the necessity of refining the NIR stellar spectral features in SPS models, such as emissions from thermally pulsating asymptotic giant branch stars or molecular absorptions from cool stars.

The Astrophysical JournalVol. 1011(2)
California Institute of Technology (US), Seoul National University (KR), Rochester Institute of Technology (US), Yonsei University (KR), University of California, Irvine (US), Korea Astronomy and Space Science Institute (KR), Sejong University (KR), Pusan National University (KR), University of California, Berkeley (US)
National Science Foundation, Smithsonian Institution, National Aeronautics and Space Administration, Alfred P. Sloan Foundation, Yale University, Carnegie Institution of Washington, Ohio State University, California Institute of Technology, Harvard University, Johns Hopkins University, New Mexico State University, Space Telescope Science Institute, Flatiron Health, National Research Foundation, École Polytechnique Fédérale de Lausanne, Yonsei University, University of Toronto, National Research Foundation of Korea, Universidad Nacional Autónoma de México, Yunnan University, Nanjing University, China National Textile and Apparel Council, Leibniz-Institut für Astrophysik Potsdam, Ministry of Science and ICT, South Korea, Max-Planck-Institut für Astronomie, University of Illinois at Urbana-Champaign, Jet Propulsion Laboratory, University of California, Los Angeles, University of Colorado Boulder, Smithsonian Astrophysical Observatory, Leibniz-Gemeinschaft, National Astronomical Observatories, Chinese Academy of Sciences
Openalex Percentile: Top 47%
Galaxies: Formation, Evolution, Phenomena
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