Fig. 1: L1544 core and illustration of the structure of interstellar medium from the CNM to the core.

a, A composite of Digitized Sky Survey 2 (DSS2) images of L1544 with the i band in red, the r band in green and the b band in blue overlaid with the HINSA and H₂ column density maps. The white dashed contours are 30%, 50%, 70% and 90% of the peak HINSA column density, and the orange contours are 2 × 10²¹ cm⁻², 4 × 10²¹ cm⁻², 6 × 10²¹ cm⁻², 8 × 10²¹ cm⁻² and 10 × 10²¹ cm⁻² for the H₂ column density. The red, green and cyan circles mark the locations and beam sizes of the FAST, Arecibo and GBT Zeeman observations, respectively. b, A composite of three 0.5 km s⁻¹ velocity slices of the Arecibo GALFA-H I images at 6.2 km s⁻¹, 6.7 km s⁻¹ and 7.3 km s⁻¹ local standard of rest (LSR) velocities in blue, green and red. The dashed rectangle shows the region of a. The two absorption dots represent the locations of quasars 3C132 and 3C133. c, Schematic view of the CNMs, the molecular envelope and the L1544 core.