HNCS and HSCN column densities (left Y-axis) and HNCS/HSCN ratio (right Y-axis) for different objects: starless/prestellar cores (TMC-1, L 1544, B 213-C16), Class 0 (IRAS 4A, L 483, B 335), Class I (B1-a), and a high-mass star forming region (Sgr B2). Black arrows indicate upper limits (B 335 and B1-a). For TMC-1 and Sgr B2, the observed column density ranges are indicated with horizontal lines. References to these data are included in Table 3.