158μm-[CII] line intensityas a function of the C157α line intensity. The line emission is separated into different groups based on known features in the maps. Top panel: line emission with velocity in the range [4, 7.5) km s⁻¹ and declination below − 5.0583°, associated with the Veil. Middle panel: line emission with velocity in the range [7.5, 12) km s⁻¹ and declination below − 5.0583°, associated with the ISF. Bottom panel: line emission at declination above − 5.0583°, associated with S279.