Zoom into the central IRDC 18310-4. The color-scale shows the 70 μm extinction feature, and the contours present the 3.2 mm PdBI continuum emission starting at 3σ and continuing in 2σ steps (1σ = 0.08 mJy beam^-1). The mm-labels, a synthesized beam and a scale-bar are shown as well. The phase reference center is close to mm1 at RA (J2000.0) 18:33:39.468 and Dec (J2000.0) − 08:21:07.65, and the primary beam of the observations with ~54′′ is larger than the shown image size.