N₂H⁺(1−0) spectra observed toward 9 filaments in Aquila. The numbers indicated on the upper right hand side of the plots, correspond to the filaments marked on the column density map of Fig. A.5 and listed in Table 1. The corresponding single-component hyperfine structure Gaussian fits are highlighted in blue. Note that the y-axis scale is not the same for all spectra, but has been adjusted to match the peak temperatures which vary between  ~ 0.2 to  > 3 K.