Theoretical Color-Magnitude Diagrams and the Star Forming Histories of Interacting Open Multi-population Model Galaxies: Bursts and Busts

This note presents theoretical color-magnitude diagrams (CMDs) and metallicity evolution for Galactic multi-population models coupled to stellar evolution models for systems undergoing stripping and re-accretion of ambient material, called ``open'' systems in our recent studies (Valle, Galli, and Shore, 2005, A&A, 435, 551). We show that the observables for such systems, in particular those related to the recovered star formation as a function of time, are ambiguous -- systems with non-monotonic star formation rates can appear as either bursting systems or galaxies with a hiatus in the star formation.