Resolved Dust-Gas-Metallicity relations in nearby spiral galaxies

Context: Understanding the interstellar medium (ISM) requires high-resolution, multi-component mapping to capture its complex physical structure. Nearby spiral galaxies, with their abundant and diverse ISM, provide an ideal laboratory for such a comprehensive analysis at sub-galactic scales. Aims: We investigate dust-to-gas (DGR) and dust-to-metal (DMR) ratios as a functions of gas-phase metallicity (Z), on spatial scales ranging from 0.6 to 2.3 kpc, in a sample of 10 nearby spiral galaxies, spanning more than an order of magnitude in stellar mass (9.7 (M*/M) at most 11.0), star formation rate (SFR, about 0.3--3, M, yr-1) and metallicity ranging from 8.3 12 + (O/H) 8.8. We explore how the DGR-Z and DMR-Z relations are shaped by the assumptions behind the CO-to-H 2 conversion factor (α CO). Methods: We homogeneously combine maps of dust, atomic gas, molecular gas, and metallicity. Motivated by the diversity in L CO(1-0)/SFR ratios and metallicity across our sample, we introduce a hybrid α CO prescription to distinguish between CO-bright and CO-dark regimes. The derived DGR-Z and DMR-Z relations are compared with other global and resolved observational results, and with the predictions of dust and chemical evolution models. Results: Both DGR-Z and DMR-Z relations are dependent on the adopted α CO prescription, and no single α CO can reproduce the properties of the entire sample, motivating the use of a hybrid approach. The DGR increases with metallicity, spanning about 1 dex across the sampled range; while the DMR remains approximately constant at (DMR) = -0.53 plus or minus 0.13, implying that about 30 % of metals are locked into dust grains. This flat behavior indicates an evolved dust phase where efficient ISM grain growth drives a saturation regime balancing dust formation and destruction.