Integrated intensity maps of the 1-0 transitions of H¹³CN and HC¹⁵N towards the inner 2′ × 2′ of L1544. The 30″ beam of the 30m telescope is shown at the bottom left of each map. The solid white contours are 30%, 60%, and 90% of the peak intensity of the N(H₂) map of L1544 computed from Herschel/SPIRE data (Spezzano et al. 2016). The dashed black contours indicate the 10σ integrated emission with steps of 10σ for H¹³CN, and 5σ with steps of 5σ for HC¹⁵N (rms_H¹³CN = 6 mK km s⁻¹, rms_HC¹⁵N = 7 mK km s⁻¹).