N₂H⁺ (1−0) IRAM 30 m VESPA data. a) Moment-zero map (using the three central hyperfine lines) of the IRAM 30 m data. Contours are 35, 45, ..., 95 percent of the value of the peak, 1.9 K km s^-1. b) Color scale: column density map. Black contours: IRAM 30 m MAMBO-II 1.2 mm dust continuum emission at an angular resolution of 21 arcsec. Contour levels are 30, 40, 50, 60, 70 and 80 percent of the peak value, 122 mJy beam^-1. c) Velocity map and d) line width map resulting from the hyperfine fit. Numbers in panel c) indicate the position of the fit spectra shown in Fig. 2 and Table 2. The HPBW of 27.8 arcsec is shown at bottom left corner of panel c).