PdBI 843 μm continuum image toward NGC 7538 IRS1. The full line contour levels start at 3σ values and continue in 1σ steps of 50 mJy beam^-1 (black contours from 3 to 9σ, white contours from 10 to 14σ). The dashed contour shows the same negative levels. The thick full line presents the 4σ contour (1σ ~ 29 mJy beam^-1) from the 1.36 mm data presented in Beuther et al. (2012a). Several potential disk and outflow axes reported in the literature are presented (Davis et al. 1998; De Buizer & Minier 2005; Sandell et al. 2009; Pestalozzi et al. 2004, 2009; Sandell & Wright 2010, see Introduction for more details). The thick line presents the axis along which the position-velocity diagrams in Fig. 4 are conducted. The northern and northwestern peaks submmN and submmNW are labeled, and the open star, the six-pointed star, and the white triangles mark the positions of the OH, H₂CO, and additional CH₃OH masers (Argon et al. 2000; Hoffman et al. 2003; Minier et al. 2001). A scale-bar and the synthesized beam (0.2″ × 0.17″) are shown as well. The 0/0 position is the phase reference center in Sect. 2.