Sub-millimetre galaxies with <i>Webb</i>
Steven Gillman, B. Gullberg, Gabe Brammer, Aswin P. Vijayan, Minju Lee, David Blánquez-Sesé, Malte Brinch, T. R. Greve, Iris Jermann, Shuowen Jin, Vasily Kokorev, Lijie Liu, G. Magdis, Francesca Rizzo, Francesco Valentino
Abstract
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 ( R e ), Sérsic index ( n ), concentration ( C ), asymmetry ( A ), clumpiness ( S ), as well as the Gini and M 20 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 1 σ scatter) of R e = 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 ( R e = 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 2 σ 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.