A parsec-scale cm-to-sub-mm SED study of the compact radio jet components in NGC 1068

Journal article, 2026

We present parsec-scale cm-to-sub-mm spectral energy distributions (SEDs) of the compact radio-jet components NE, C, S2, and S3 in the Seyfert 2 galaxy NGC 1068. Matched-(Formula presented)  e-MERLIN, VLA, and ALMA imaging spans 4.5–706 GHz at a common 0.06-arcsec resolution and 15–3300 k(Formula presented)  (Formula presented) -coverage. Spatial-blending tests show weak inter-component covariance, less than 1 per cent direct neighbour-induced flux transfer, and a maximum S2 perturbation of 8.4 per cent across the 18.9–22.9-GHz turnover region, corresponding to (Formula presented) GHz or (Formula presented). Bayesian MCMC modelling with synchrotron emission, free–free emission, and free–free absorption yields steep intrinsic synchrotron indices, (Formula presented) to (Formula presented). The cut-off is lowest in C, (Formula presented) GHz. NE and S3 have measured cut-offs of (Formula presented) and (Formula presented) GHz, respectively, whereas S2 yields only the lower limit (Formula presented) GHz. A partial-covering absorber is favoured for all four components ((Formula presented) –30.1; (Formula presented) –28.0). NE, C, and S3 have comparable clump-opacity scales, (Formula presented) –12 GHz, and covering factors, (Formula presented) –0.53, with C additionally requiring diffuse absorption. S2 is the clear exception, with (Formula presented) GHz and (Formula presented) ; its opacity scale differs from those of the other components by approximately 4.8–(Formula presented). The results support a sightline-dependent ionized medium in which S2 intersects the densest and most strongly covering absorber, plausibly near the torus–inner-narrow-line region interface. No off-nuclear component requires a significant mm–sub-mm excess above the synchrotron model.