2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/166672We study algebraic (Artin) stacks over $\bar{\mathcal M}_g$ giving a functorial way of compactifying the relative degree $d$ Picard variety for families of stable curves. We also describe for every $d$ the locus of genus $g$ stable curves over which we get Deligne-Mumford stacks strongly representable over $\bar{\mathcal M}_g$.21 pages; To appear in Math. ZeitAlgebraic Geometry14H10; 14H60; 14H40text