Upper pannels: HfS fit of the hyperfine structure of N₂H⁺ (1−0) IRAM 30 m spectral data at different positions of the core (labeled in Fig. 1c). Black and red lines are the observational data and the fit, respectively. Lower panels: ARTIST simulated N₂H⁺ (1−0) spectral data (see Sect. 4.2). Black and blue lines are the observational and simulated data, respectively. We note that the simulated core from ARTIST is spherically symmetric. The discrepancies between the observational and the simulated spectra in panel (4) may be due to the slightly elongated shape of the core towards the west.