Literature comparison of integrated intensities for the J = 1 − 0 transition of (from top to bottom): HCN, HNC, HCO⁺, and N₂H⁺ emission compared to ¹²CO. We show the SWAN integrated emission (light-shaded area) for the full FoV (squares), the central 1 kpc (triangle), and the remaining disk (circle). These values are obtained by integrating emission from pixels where both the line emission and ¹²CO emission is significantly detected (> 3σ). The distribution of pixels in the full FoV is added as violins. The error bars correspond to the difference between this calculation (both ¹²CO and the line are significantly detected) and when instead using pixels where ¹²CO is significantly detected. Average literature values (horizontal dashed lines, calculated on a linear scale) are based on values from Milky Way (Pety et al. 2017; Barnes et al. 2020; Jones et al. 2012) and extragalactic sources: M51 studies at lower resolution (Watanabe et al. 2014) and in the outer spiral arm (Chen et al. 2017); different galaxy averages from EMPIRE (Jiménez-Donaire et al. 2019); ∼100 pc studies in M33 (Buchbender et al. 2013), M31 (Brouillet et al. 2005) and NGC6946 (Eibensteiner et al. 2022); ∼10 pc observation in the LMC (Nishimura et al. 2016a) and 80 pc in the dwarf galaxy IC10 (Nishimura et al. 2016b); ∼15 − 19″ in three nearby galaxies (Takano et al. 2019) and upper limits from z ∼ 3 galaxies (Rybak et al. 2022). The values are basically sorted by their physical resolution from a few parsecs in the Milky Way (left) to several kiloparsecs in external galaxies (right).