MEGA: Spectrophotometric Spectral Energy Distribution Fitting of Little Red Dots Detected in JWST MIRI
14 affiliations
- 1Texas A&M University
- 2University of Kansas
- 3University of Edinburgh
- 4NASA Goddard Space Flight Center
- 5The University of Texas at Austin
- 6University of the Pacific
- 7Rochester Institute of Technology
- 8Colby College
- 9Space Telescope Science Institute
- 10NASA-Goddard Space Flight Center
- 11Center for Astrophysics ∣Harvard & Smithsonian
- 12Harvard University
- 13SRON Netherlands Institute for Space Research
- 14University of Groningen
Abstract
We analyze eight spectroscopically confirmed little red dots (LRDs) at redshifts z = 5.1–8.7 with JWST/NIRCam, NIRSpec, and MIRI data. The LRDs have red NIRCam colors, F150W − F444W > 1, but flat NIRCam − MIRI colors, −0.5 < F444W − F770W < 0.5, suggesting weak warm/hot dust components. The LRDs have −1.0 < F1000W − F1500W < 1.1, suggestive of nonuniform rest near-IR properties within the sample. We model the spectral energy distributions (SEDs) of the LRDs using the CIGALE and P rospector codes to assess how the differing templates impact the interpretation for LRDs for cases of: (1) models with star-forming (SF) stellar populations only; (2) active galactic nuclei (AGN)-dominated models; and (3) composite AGN and SF models. Using the Bayesian information criterion, we find that six of the eight LRDs favor AGN models compared to SF models, though no model reproduces all of the observed properties. Two LRDs with pronounced Balmer breaks and broad H α have SEDs that are reproduced with hot, dense-gas ( log T / K = 5 – 5.7 , log n / cm − 3 = 9 – 11 ) models with low dust attenuation ( A ( V ) ≃ 0.5 mag). However, these models require an additional thermal component (800–1400 K) to account for the MIRI data, and fail to reproduce the rest-UV and narrow [O iii ] emission. The total bolometric emission from the dense-gas models, and possibly CIGALE AGN models, appears consistent with literature constraints in the far-IR and radio, and requires log L bol / L ⊙ < 12 . These results suggest that our LRDs cannot be modeled entirely with standard templates, but instead require a novel treatment of gas conditions, AGN, and star formation.
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BibTeX
@article{ronayne2026mega,
title = {{MEGA: Spectrophotometric Spectral Energy Distribution Fitting of Little Red Dots Detected in JWST MIRI}},
author = {Kaila Ronayne and Casey Papovich and Allison Kirkpatrick and Bren E. Backhaus and Fergus Cullen and Lu Shen and Micaela B. Bagley and Guillermo Barro and Steven L. Finkelstein and Kurt Hamblin and Jeyhan S. Kartaltepe and Dale D. Kocevski and Anton M. Koekemoer and Erini Lambrides and Fabio Pacucci and Guang Yang},
journal = {The Astrophysical Journal},
year = {2026},
month = may,
doi = {10.3847/1538-4357/ae5e6b},
url = {https://doi.org/10.3847/1538-4357/ae5e6b},
note = {CC BY},
}
RIS
TY - JOUR
TI - MEGA: Spectrophotometric Spectral Energy Distribution Fitting of Little Red Dots Detected in JWST MIRI
AU - Kaila Ronayne
AU - Casey Papovich
AU - Allison Kirkpatrick
AU - Bren E. Backhaus
AU - Fergus Cullen
AU - Lu Shen
AU - Micaela B. Bagley
AU - Guillermo Barro
AU - Steven L. Finkelstein
AU - Kurt Hamblin
AU - Jeyhan S. Kartaltepe
AU - Dale D. Kocevski
AU - Anton M. Koekemoer
AU - Erini Lambrides
AU - Fabio Pacucci
AU - Guang Yang
PY - 2026
DA - 2026/05/28
JO - The Astrophysical Journal
DO - 10.3847/1538-4357/ae5e6b
UR - https://doi.org/10.3847/1538-4357/ae5e6b
AB - We analyze eight spectroscopically confirmed little red dots (LRDs) at redshifts z = 5.1–8.7 with JWST/NIRCam, NIRSpec, and MIRI data. The LRDs have red NIRCam colors, F150W − F444W > 1, but flat NIRCam − MIRI colors, −0.5 < F444W − F770W < 0.5, suggesting weak warm/hot dust components. The LRDs have −1.0 < F1000W − F1500W < 1.1, suggestive of nonuniform rest near-IR properties within the sample. We model the spectral energy distributions (SEDs) of the LRDs using the CIGALE and P rospector codes to assess how the differing templates impact the interpretation for LRDs for cases of: (1) models with star-forming (SF) stellar populations only; (2) active galactic nuclei (AGN)-dominated models; and (3) composite AGN and SF models. Using the Bayesian information criterion, we find that six of the eight LRDs favor AGN models compared to SF models, though no model reproduces all of the observed properties. Two LRDs with pronounced Balmer breaks and broad H α have SEDs that are reproduced with hot, dense-gas ( log T / K = 5 – 5.7 , log n / cm − 3 = 9 – 11 ) models with low dust attenuation ( A ( V ) ≃ 0.5 mag). However, these models require an additional thermal component (800–1400 K) to account for the MIRI data, and fail to reproduce the rest-UV and narrow [O iii ] emission. The total bolometric emission from the dense-gas models, and possibly CIGALE AGN models, appears consistent with literature constraints in the far-IR and radio, and requires log L bol / L ⊙ < 12 . These results suggest that our LRDs cannot be modeled entirely with standard templates, but instead require a novel treatment of gas conditions, AGN, and star formation.
SN - 0004-637X
SN - 1538-4357
ER -