Ubiquitous nuclear disks and bars embedded in massive galaxies in the cosmic morning
Abstract
The morphology of the central regions of high-redshift galaxies remains relatively unexplored, while recent case studies suggest that giant disks can emerge without first developing a prominent central spheroid. Here, we investigate the inner structures of a mass-complete sample of 45 massive galaxies at z=3 in the TNG50 simulation. Through double-Sérsic profile decomposition, isodensity ellipse fitting, intrinsic three-dimensional shape measurements, and stellar kinematics, we find that these central structures are ubiquitously flattened and rotation-supported with low Sérsic indices (n ≲ 1). This indicates that the central regions are predominantly nuclear disks and bars rather than bulges. Tracking their evolution, we show that these nuclear disks and bars emerge during gas-rich compaction and do not transform into spheroidal and dispersion-dominated systems until z ≲ 1, before which extended stellar disks have already developed. Our results suggest that massive disks can assemble around rotation-supported centers and bulge-deficient massive galaxies may be a common outcome of galaxy evolution.
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BibTeX
@misc{luo2026ubiquitous,
title = {{Ubiquitous nuclear disks and bars embedded in massive galaxies in the cosmic morning}},
author = {Jianyuan Luo and Fangzhou Jiang and Jinning Liang and Boris S. Kalita and Pinsong Zhao and Jinyi Shangguan and Bingcheng Jin and Zeyu Gao and Weichen Wang and Luis C. Ho and Yingjie Peng},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.27460},
eprint = {2609.27460},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.27460},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Ubiquitous nuclear disks and bars embedded in massive galaxies in the cosmic morning
AU - Jianyuan Luo
AU - Fangzhou Jiang
AU - Jinning Liang
AU - Boris S. Kalita
AU - Pinsong Zhao
AU - Jinyi Shangguan
AU - Bingcheng Jin
AU - Zeyu Gao
AU - Weichen Wang
AU - Luis C. Ho
AU - Yingjie Peng
PY - 2026
DA - 2026/09/23
PB - arXiv
DO - 10.48550/arxiv.2609.27460
UR - https://arxiv.org/abs/2609.27460
AB - The morphology of the central regions of high-redshift galaxies remains relatively unexplored, while recent case studies suggest that giant disks can emerge without first developing a prominent central spheroid. Here, we investigate the inner structures of a mass-complete sample of 45 massive galaxies at z=3 in the TNG50 simulation. Through double-Sérsic profile decomposition, isodensity ellipse fitting, intrinsic three-dimensional shape measurements, and stellar kinematics, we find that these central structures are ubiquitously flattened and rotation-supported with low Sérsic indices (n ≲ 1). This indicates that the central regions are predominantly nuclear disks and bars rather than bulges. Tracking their evolution, we show that these nuclear disks and bars emerge during gas-rich compaction and do not transform into spheroidal and dispersion-dominated systems until z ≲ 1, before which extended stellar disks have already developed. Our results suggest that massive disks can assemble around rotation-supported centers and bulge-deficient massive galaxies may be a common outcome of galaxy evolution.
ER -