2023ApJ...958L..26H

Dusty star-forming galaxies (DSFGs) are among the most massive and active star-forming galaxies during the cosmic noon. Theoretical studies have proposed various formation mechanisms of DSFGs, including major merger-driven starbursts and secular star-forming disks. Here, we report J0107a, a bright (∼8 mJy at observed-frame 888 μm) DSFG at z = 2.467 that appears to be a gas-rich massive disk and might be an extreme case of the secular disk scenario. J0107a has a stellar mass M_⋆ ∼ 5 × 10¹¹M_⊙, molecular gas mass M_mol ≳ 10¹¹M_⊙, and a star formation rate of ∼500M_⊙ yr^–1. J0107a does not have a gas-rich companion. The rest-frame 1.28 μm JWST NIRCam image of J0107a shows a grand-design spiral with a prominent stellar bar extending ∼15 kpc. The Atacama Large Millimeter/submillimeter Array Band 7 continuum map reveals that the dust emission originates from both the central starburst and the stellar bar. 3D disk modeling of the CO(4-3) emission line indicates a dynamically cold disk with rotation-to-dispersion ratio ${V}_{\max }/\sigma \sim 8$. The results suggest a bright DSFG may have a nonmerger origin, and its vigorous star formation may be triggered by the bar and/or rapid gas inflow.