SDSS-V LVM: Spatial Resolution Effects on Diagnostic Diagrams in the Magellanic Clouds

Abstract

We investigate how spatial resolution affects emission-line diagnostics in the interstellar medium (ISM) of the Small and Large Magellanic Clouds (SMC and LMC) using SDSS Local Volume Mapper (LVM) data obtained at and degraded to 19, 42, 170 pc (for the SMC) and 17, 68, 272 pc (for the LMC), respectively. We compare the distributions of strong emission-line ratios through 1D and 2D Kolmogorov Smirnov tests. We deduced that diagnostics involving ionization and density sensitive ratios such as [OIII]λ5007/H\b{eta}, [SII]λλ6717+6731/Hα and [NII]λ6584/Hα are the most strongly impacted by resolution loss in this order. The SMC shows significant deviations even from intermediate scales (42 pc), whereas for the LMC, the coarsest resolution (272 pc) remains relatively stable, indicating that the SMC is intrinsically more affected by spatial mixing. Resolution degradation produces a marked homogenization effect: extreme values present at the finest scales are progressively diluted, causing diagnostic diagrams to converge toward their mean loci. Diffuse ionized gas is particularly sensitive to this mixing, while Hα selected ionized regions exhibit more robust behavior across resolutions. The sensitivity of diagnostic diagrams involving emission-line ratios, equivalent widths, and kinematic properties varies with both spatial resolution and galaxy, with the SMC generally showing stronger changes than the LMC. Our results demonstrate that sub-50 pc resolution is required to resolve the detailed structure of low-metallicity galaxies, and they highlight at least the need for careful interpretation of line-ratio diagnostics in extragalactic studies where coarse spatial resolution is unavoidable.