Continuum maps of G135.27 at 233 GHz (a) and 229 GHz (b) in gray scale, extracted from setups S1-UI-CO and S2-LI-CO, respectively. Contour levels start at 3σ and increase by a factor of 2, where σ = 0.13 and 0.12 mJy beam⁻¹, respectively. Negative contours at −3σ are shown as dashed lines. The black crosses mark three continuum peaks of G135.27, labeled MM1, MM2, and MM3 (see Sect. 3.1), with the peak flux density of MM1 indicated in the upper right corner. The empty circles denote the positions of H₂O masers (Hachisuka et al. 2009), with blue and red indicating maser spots blue- and redshifted with respect to the source systemic velocity of −71.7 km s⁻¹, respectively (Blair et al. 2008). The beam size (HPBW) is displayed as an ellipse in the bottom left corner. The offsets are defined with respect to the phase center (see Sect. 2.2). The maps are not corrected for primary-beam attenuation.