Large-scale gravitational field (red arrows) and magnetic field (cyan segments from PLANCK) overlaid on the column density map derived from Herschel 5-band continuum data. The white contours are the JCMT 850 μm continuum as shown in Figure 3. The yellow contours mark column density levels of 3.5 and 4.8 × 10²² cm⁻², tracing the outer large-scale north–south filament that is hosting SDC13. The large-scale gravitational field is first converging onto the large-scale north–south filament in the outer part, and then pointing toward the south along the filament.