Abstract
We examine the morphological and kinematical properties of SPT-2147, a strongly lensed, massive, dusty, star-forming galaxy at $z = 3.762$. Combining data from JWST, Hubble Space Telescope, and ALMA, we study the galaxy's stellar emission, dust continuum, and gas properties. The imaging reveals a central bar structure in the stars and gas embedded within an extended disc with a spiral arm-like feature. The kinematics confirm the presence of the bar and of the regularly rotating disc. Dynamical modelling yields a dynamical mass, ${M}_{\rm dyn} = (9.7 \pm 2.0) \times 10^{10}$${\rm M}_{\odot }$, and a maximum rotational velocity to velocity dispersion ratio, $V / \sigma = 9.8 \pm 1.2$. From multiband imaging we infer, via spectral energy distribution fitting, a stellar mass, ${M}_{\star } = (6.3 \pm 0.9) \times 10^{10}$$\rm {M}_{\odot }$, and a star formation rate, ${\rm SFR} = 781 \pm 99$${\rm {\rm M}_{\odot } yr^{-1}}$, after correcting for magnification. Combining these measurements with the molecular gas mass, we derive a baryonic-to-total mass ratio of ${M}_{\rm bar} / {M}_{\rm dyn} = 1.1 \pm 0.3$ within 4.0 kpc. This finding suggests that the formation of bars in galaxies begins earlier in the history of the Universe than previously thought and can also occur in galaxies with elevated gas fractions.
