Maps of observed and derived properties of NGC 4321. Top: Convolved and re-gridded SDSS r band, logarithms of stellar mass surface density (Σ_star), SFR surface density (Σ_SFR), dust mass surface density (Σ_dust), as well as SED-fitting-derived attenuation in the V band (A_V, SED), from left to right. Bottom: Surface density of atomic gas mass (Σ_HI), surface density of molecular gas mass (Σ_H2), logarithm of the total gas mass surface density (Σ_gas), dust-to-gas ratio and attenuation in the V band as derived by the BD (A_V, BD), from left to right. All maps are at a resolution of 18″. Grey points correspond to pixels that are rejected because they do not have a sufficient number of data points in the FIR regime (see Sect. 2.1.1) or because they are unreliable (see Sect. 2.3 for more details). The Σ_HI and Σ_H2 maps extend up to their corresponding 3σ limit. In the Σ_HI, Σ_H2, and A_V, BD maps pixels that correspond to the areas that are excluded by the SED-fitting analysis are plotted with smaller dots. In the log₁₀Σ_gas map, pixels excluded by the SED-fitting analysis and having both H I and CO detection are depicted by smaller squares, while pixels with only H I and not CO are plotted with dots. In the dust-to-gas ratio maps, we limit the colour-coding to the 5th–95th percentile range for illustrative purposes. Contours are taken from the log₁₀Σ_dust [M_⊙ pc⁻²] maps with a lowest contour at –1.5 and linear spacing with the highest at 0.