HCN spectrum taken along the minor axis. Left: bar sight lines in NGC 253. We label major and minor axes. Colored points are sight lines showing enhanced HCN/CO(2–1) emission in the direction of the SW streamer (Walter et al. 2017) and that contribute to the bimodality seen in Figure 4. Colors correspond to their HCN/CO(2–1) intensity ratio shown in the colorbar. Right: HCN spectra toward the data points located along the minor axis in NGC 253 shown on the left. Each spectrum is colored by the HCN/CO(2–1) ratio shown on the colorbar. All these data points are located along the SW streamer (Walter et al. 2017). The black dashed line shows NGC 253 systemic velocity of 243 km s⁻¹ (see Table 1). The black solid line represents the υ_lsr = 200 km s⁻¹ velocity at which Walter et al. (2017) observed the outflowing component in CO(1–0) emission.