TY - JOUR
T1 - JWST/MIRI Reveals the True Number Density of Massive Galaxies in the Early Universe
AU - Wang, Tao
AU - Sun, Hanwen
AU - Zhou, Luwenjia
AU - Xu, Ke
AU - Cheng, Cheng
AU - Li, Zhaozhou
AU - Chen, Yangyao
AU - Mo, H. J.
AU - Dekel, Avishai
AU - Yang, Tiancheng
AU - Wang, Yijun
AU - Chen, Longyue
AU - Zheng, Xianzhong
AU - Cai, Zheng
AU - Elbaz, David
AU - Dai, Y. S.
AU - Huang, J. S.
N1 - Publisher Copyright:
© 2025. The Author(s). Published by the American Astronomical Society.
PY - 2025/7/20
Y1 - 2025/7/20
N2 - Early JWST studies reporting an unexpected abundance of massive galaxies at z ∼ 5-8 challenge galaxy formation models in the ΛCDM framework. Previous stellar mass (M⋆) estimates suffered from large uncertainties due to the lack of rest-frame near-infrared data. Using deep JWST/NIRCam and Mid-Infrared Instrument (MIRI) photometry from Public Release IMaging for Extragalactic Research, we systematically analyze massive galaxies at z ∼ 3-8, leveraging rest-frame ≳1 μm constraints. We find MIRI is critical for robust M⋆ measurements for massive galaxies at z > 5: excluding MIRI overestimates M⋆ by ∼0.4 dex on average for M⋆ > 1010M⊙ galaxies, with no significant effects at lower masses. This reduces number densities of M⋆ > 1010M⊙ (1010.3M⊙) galaxies by ∼36% (55%). MIRI inclusion also reduces “Little Red Dot” (LRD) contamination in massive galaxy samples, lowering the LRD fraction from ∼32% to ∼13% at M⋆ > 1010.3M⊙. Assuming pure stellar origins, LRDs exhibit M⋆ ∼ 109-10.5M⊙ with MIRI constraints, rarely exceeding 1010.5M⊙. Within standard ΛCDM, our results indicate a moderate increase in the baryon-to-star conversion efficiency (ϵ) toward higher redshifts and masses at z > 3. For the most massive z ∼ 8 galaxies, ϵ ∼ 0.3, compared to ϵ ≲ 0.2 for typical galaxies at z < 3. This result is consistent with models where high gas densities and short free-fall times suppress stellar feedback in massive high-z halos.
AB - Early JWST studies reporting an unexpected abundance of massive galaxies at z ∼ 5-8 challenge galaxy formation models in the ΛCDM framework. Previous stellar mass (M⋆) estimates suffered from large uncertainties due to the lack of rest-frame near-infrared data. Using deep JWST/NIRCam and Mid-Infrared Instrument (MIRI) photometry from Public Release IMaging for Extragalactic Research, we systematically analyze massive galaxies at z ∼ 3-8, leveraging rest-frame ≳1 μm constraints. We find MIRI is critical for robust M⋆ measurements for massive galaxies at z > 5: excluding MIRI overestimates M⋆ by ∼0.4 dex on average for M⋆ > 1010M⊙ galaxies, with no significant effects at lower masses. This reduces number densities of M⋆ > 1010M⊙ (1010.3M⊙) galaxies by ∼36% (55%). MIRI inclusion also reduces “Little Red Dot” (LRD) contamination in massive galaxy samples, lowering the LRD fraction from ∼32% to ∼13% at M⋆ > 1010.3M⊙. Assuming pure stellar origins, LRDs exhibit M⋆ ∼ 109-10.5M⊙ with MIRI constraints, rarely exceeding 1010.5M⊙. Within standard ΛCDM, our results indicate a moderate increase in the baryon-to-star conversion efficiency (ϵ) toward higher redshifts and masses at z > 3. For the most massive z ∼ 8 galaxies, ϵ ∼ 0.3, compared to ϵ ≲ 0.2 for typical galaxies at z < 3. This result is consistent with models where high gas densities and short free-fall times suppress stellar feedback in massive high-z halos.
UR - https://www.scopus.com/pages/publications/105011202867
U2 - 10.3847/2041-8213/adebe7
DO - 10.3847/2041-8213/adebe7
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AN - SCOPUS:105011202867
SN - 2041-8205
VL - 988
JO - Astrophysical Journal Letters
JF - Astrophysical Journal Letters
IS - 1
M1 - L35
ER -