A Rest-frame K -band View of Bulge Growth in Massive Star-forming Galaxies at z ∼ 2
- 1Hokkai-Gakuen University
Abstract
We study bulge formation in 16 massive dusty star-forming galaxies at z ∼ 2 by combining JWST MIRI F770W imaging, NIRCam imaging in eight bands, and Atacama Large Millimeter/submillimeter Array (ALMA) 870 μ m data. At the median redshift of z = 2.18, the F770W band probes the rest-frame 2.4 μ m light, close to the rest-frame K band, and traces the stellar mass distribution with much less dust attenuation than the NIRCam bands. The effective radii measured in F770W agree with those of the 870 μ m dust emission, with a median ratio of 0.95, and are typically 23% smaller than those in F444W. The rest-frame K -band imaging is, therefore, essential to measure the true extent of the stellar mass, which is as compact as the dusty star-forming regions. In stacks of the 16 galaxies at a matched resolution, the 870 μ m and F770W profiles agree closely out to 8 kpc, and a bulge plus disk decomposition of the F770W stack gives a bulge-to-total ratio of 0.50. Fitting the spectral energy distributions (SEDs) in radial bins with CIGALE, we find that the attenuation decreases from A V = 3.7 mag at the center to 1.9 mag at r ≳ 7 kpc, while the specific star formation rate profile is flat. In most of the galaxies, the bulge is already in place inside the dusty core. In two galaxies, by contrast, the 870 μ m emission is 3–6 times more compact than the F770W light, which suggests that they are still in the bulge-building compaction phase. Our sample may, thus, catch massive galaxies in several phases of bulge formation.
Related
- A SHARP Look at Quenching and Bulge-Disk Growth in Massive Galaxies at Cosmic Noon
- The Stellar Populations and Rest-frame Colors of Star-forming Galaxies at z ≈ 8: Exploring the Impact of Filter Choice and Star Formation History Assumption with JADES
- GASTRO Library. II. Exploring Chemical Bimodalities in Disk Galaxies with GSE-like Mergers and Massive Star-forming Clumps
- TRICEPS. I. Tracing cold gas, dust, and stars at sub-kpc scales in massive star-forming galaxies at z = 4-5
- GA-NIFS: High prevalence of dusty and metal-enriched outflows in massive and luminous star-forming galaxies at z ∼ 3–9
BibTeX
@article{tadaki2026restframe,
title = {{A Rest-frame K -band View of Bulge Growth in Massive Star-forming Galaxies at z ∼ 2}},
author = {Ken-ichi Tadaki},
journal = {The Astrophysical Journal},
year = {2026},
month = oct,
doi = {10.3847/1538-4357/aea6de},
url = {https://iopscience.iop.org/article/10.3847/1538-4357/aea6de},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - A Rest-frame K -band View of Bulge Growth in Massive Star-forming Galaxies at z ∼ 2
AU - Ken-ichi Tadaki
PY - 2026
DA - 2026/10/14
JO - The Astrophysical Journal
DO - 10.3847/1538-4357/aea6de
UR - https://iopscience.iop.org/article/10.3847/1538-4357/aea6de
AB - We study bulge formation in 16 massive dusty star-forming galaxies at z ∼ 2 by combining JWST MIRI F770W imaging, NIRCam imaging in eight bands, and Atacama Large Millimeter/submillimeter Array (ALMA) 870 μ m data. At the median redshift of z = 2.18, the F770W band probes the rest-frame 2.4 μ m light, close to the rest-frame K band, and traces the stellar mass distribution with much less dust attenuation than the NIRCam bands. The effective radii measured in F770W agree with those of the 870 μ m dust emission, with a median ratio of 0.95, and are typically 23% smaller than those in F444W. The rest-frame K -band imaging is, therefore, essential to measure the true extent of the stellar mass, which is as compact as the dusty star-forming regions. In stacks of the 16 galaxies at a matched resolution, the 870 μ m and F770W profiles agree closely out to 8 kpc, and a bulge plus disk decomposition of the F770W stack gives a bulge-to-total ratio of 0.50. Fitting the spectral energy distributions (SEDs) in radial bins with CIGALE, we find that the attenuation decreases from A V = 3.7 mag at the center to 1.9 mag at r ≳ 7 kpc, while the specific star formation rate profile is flat. In most of the galaxies, the bulge is already in place inside the dusty core. In two galaxies, by contrast, the 870 μ m emission is 3–6 times more compact than the F770W light, which suggests that they are still in the bulge-building compaction phase. Our sample may, thus, catch massive galaxies in several phases of bulge formation.
SN - 0004-637X
SN - 1538-4357
ER -