We utilised the unprecedented depth and resolution of recent early-release science (ERS) JWST observations to define the near-infrared counterparts of sub-millimetre galaxies (SMGs). We identified 45 SCUBA-2 SMG positions within the Cosmic Evolution Early Release Science (CEERS) survey JWST/NIRCam fields. Through an analysis of multi-wavelength p-values, NIRCam colours and predicted SCUBA-2 fluxes, we define 43 JWST/NIRCam counterparts to the SCUBA-2 SMGs, finding a 63 per cent agreement with those identified in prior HST studies. Using EaZy-py, we fitted the available HST and JWST observations to quantify the photometric redshifts of the NIRCam-SMGs, establishing a broad range of redshift from z ≈ 0.2–5.4 with a median of z ≈ 2.29, in agreement with other studies of SMGs. We identified significant variations in the morphology of the NIRCam-SMGs from isolated discs and spheroidal galaxies to irregular interacting systems. We analysed their rest-frame optical and near-infrared morphological properties (e.g. effective radius (Re), Sérsic index (n), concentration (C), asymmetry (A), clumpiness (S), as well as the Gini and M20 parameters), finding, on average, late-type disc-like morphologies with large scatter into the intermediate and merger regions of the non-parametric parameter space. For the non-merging galaxies, we find a median rest-frame optical size and Sérsic index (and 1σ scatter) of Re = 3.10 ± 1.67 kpc and n = 0.96 ± 0.66. Whilst in the rest-frame near-infrared, we establish more compact, higher Sérsic index morphologies (Re = 1.64 ± 0.97, n = 1.85 ± 0.63). We further establish that both the rest-frame optical and near-infrared effective radii correlate negatively (at a 2σ level) with redshift, whilst the Sérsic index remains constant with cosmic time. Our results are consistent with the picture of inside-out galaxy evolution, with more centrally concentrated older stellar populations, and more extended, younger star-forming regions whose stellar emission is heavily attenuated in the central regions.

We present a 1.1 mm stacking analysis of moderately massive (log(M*/M⊙) = 10.7 ± 0.2) quiescent galaxies (QGs) at ⟨z⟩∼1.5, searching for cold dust continuum emission, which serves as an excellent tracer of dust and gas mass. Using both the recent GOODS-ALMA survey, as well as the full suite of ALMA Band-6 ancillary data in the GOODS-S field, we report the tentative detection of a dust continuum equivalent of the dust mass log(Mdust/M⊙) = 7.47 ± 0.13 and gas mass log(Mgas/M⊙) = 9.42 ± 0.14. The emerging gas fraction is fgas = 5.3 ± 1.8%, consistent with the results of previous stacking analyses based on lower resolution sub(mm) observations. Our results support the scenario where high-z QGs exhibit a larger fgas value by one order of magnitude compared to their local counterparts and have experienced quenching with a non-negligible gas reservoir in their interstellar medium, namely, with gas retention. Our subsequent analysis yields an anti-correlation between the fgas and the stellar mass of QGs, especially in the high-mass end where galaxies reside in the most massive halos. The fgas − M* anti-correlation promotes the selection bias as a possible solution to the tension between the stacking results pointing towards gas retention in high-z QGs of moderate M* and studies of individual targets that favour a fully depleted ISM in massive (log(M*/M⊙) > 11.2) high-z QGs.