Gallery of integrated intensity maps (in K km s⁻¹ ) of observed lines used in this work. The line name is indicated on the top of each panel while their beam is shown in the lower right corner. The star indicates the position of L1489 IRS. The cyan contour corresponds to the targeted emission for the analysis (see Sect. 3.2). Top row: Single-field combined (IRAM-30m + NOEMA) observations of C₂H. Middle row: IRAM-30m (columns 1 to 5) and combined (column 6) observations of HC₃N. Bottom row: Mosaic (first and second column) and single-field (third and fourth column) combined observations of c–C₃H₂.