ALESS-JWST: Joint (Sub)kiloparsec JWST and ALMA Imaging of <i>z</i> ~ 3 Submillimeter Galaxies Reveals Heavily Obscured Bulge Formation Events

Abstract We present JWST NIRCam imaging targeting 13 z ~ 3 infrared-luminous ( L IR ∼ 5 × 10 12 L ⊙ ) galaxies from the ALESS survey with uniquely deep, high-resolution (0 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover> <mml:mrow> <mml:mo>.</mml:mo> </mml:mrow> <mml:mrow> <mml:mtext>″</mml:mtext> </mml:mrow> </mml:mover> </mml:math> 08–0 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover> <mml:mrow> <mml:mo>.</mml:mo> </mml:mrow> <mml:mrow> <mml:mo accent="false">″</mml:mo> </mml:mrow> </mml:mover> </mml:math> 16) Atacama Large Millimeter/submillimeter Array 870 μ m imaging. The 2.0–4.4 μ m (observed frame) NIRCam imaging reveals the rest-frame near-infrared stellar emission in these submillimeter-selected galaxies at the same (sub)kiloparsec resolution as the 870 μ m dust continuum. The newly revealed stellar morphologies show striking similarities with the dust continuum morphologies at 870 μ m, with the centers and position angles agreeing for most sources, clearly illustrating that the spatial offsets reported previously between the 870 μ m and Hubble Space Telescope morphologies were due to strong differential dust obscuration. The F444W sizes are 78% ± 21% larger than those measured at 870 μ m, in contrast to recent results from hydrodynamical simulations that predict larger 870 μ m sizes. We report evidence for significant dust obscuration in F444W for the highest-redshift sources, emphasizing the importance of longer-wavelength MIRI imaging. The majority of the sources show evidence that they are undergoing mergers/interactions, including tidal tails/plumes—some of which are also detected at 870 μ m. We find a clear correlation between NIRCam colors and 870 μ m surface brightness on ∼1 kpc scales, indicating that the galaxies are primarily red due to dust—not stellar age—and we show that the dust structure on ∼kpc scales is broadly similar to that in nearby galaxies. Finally, we find no strong stellar bars in the rest-frame near-infrared, suggesting the extended bar-like features seen at 870 μ m are highly obscured and/or gas-dominated structures that are likely early precursors to significant bulge growth.