Calculated brightness temperature ratios for HCN 4–3/1–0 (left), HNC 4–3/1–0 (center), and HC₃N 37–36/10–9 (right). Contours show modeled ratios assuming a column density of 10¹³ cm⁻² and a line width of 2 km s⁻¹ for all three molecular species. The light blue shaded region shows the temperature range derived from the HCN/HNC ratio, with the blue line indicating the mean gas temperature. The gray shaded area shows the density range for the N-S ridge derived from envelope models.