Cosmology from a running vacuum model driven by a scalar field

Abstract: The possibility that the vacuum energy density $\rho_\Lambda$ is, indeed, varying in time, has been investigated lately from the running vacuum models perspective. Motivated by such models, in the present work, we relate the decaying vacuum energy $\rho_\Lambda(t)$ with a scalar field $\phi$. We derive the equations of motion from such a premise and implement the first-order formalism in order to obtain analytical solutions to the cosmological parameters. We show that those are in agreement with recent Planck observational data. We discuss the physical consequences of having $\rho_\Lambda(t)$ related to $\phi$.