Tropicalization of the universal Jacobian

In this article we provide a stack-theoretic framework to study the universal tropical Jacobian over moduli space of curves. We develop two approaches process tropicalization compactified curves -- one from logarithmic and other non-Archimedean analytic point view. The central result both points view is that maps in each contexts are compatible with tautological morphisms. sequel will use techniques developed here explicit polyhedral models for Picard variety.