J0107a: A Barred Spiral Dusty Star-forming Galaxy at z = 2.467

Abstract

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 × 10¹¹ M _⊙, molecular gas mass M _mol ≳ 10¹¹ M _⊙, 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.