Does galaxy-scale compactness regulate nebular electron density? A cross-scale test with DESI

Nebular electron density, $n_e$, traces ionized gas in small-scale H\,{\sc ii} regions and diffuse ionized structures, whereas galaxy stellar surface density, $Σ_\star$, measures compactness on kpc scales. Whether these quantities are correlated is therefore a cross-scale question rather than a geom