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Galaxy Evolutionary Synthesis Models
help you understand your data on star clusters and galaxies from the early universe until today in terms of their relevant physical and chemical properties and their evolutionary state.

Resolved stellar populations vs. integrated light:
Accuracies and limitations in the recovery of Star Formation Histories

An important methodological study - that is only possible with GALEV as the only evolutionary synthesis code that can describe the evolution of a resolved stellar population in terms of CMDs and, at the same time, the evolution of its integrated light - is the comparison to what accuracy and how far back in time the SFH of a composite stellar population can be reconstructed using these different approaches. While CMD analyses are limited to low stellar density systems in the local group, integrated light studies are the only approach to SFHs of distant galaxies. Hence, a comparison of both methods against each other is of prime importance. We have recently begun this in a two-fold way, on the basis of models only (with simplified toy SFHs) and in comparison to a field in the LMC bar that has both, a very deep CMD from HST and a VLT trailed slit integrated spectrum of exactly the same field we obtained (coll. with D. Alloin, ESO, C. Gallart, IAC, P. Demarque, Yale, and S. Yi, Korea). The surprising result of the latter study was that while, clearly, CMD analyses yield a finer time resolution in the SFH during the last few hundred Myr, both methods have very similar power and limitations for longer lookback times. Analyses of multi-band spectral energy distributions including UV or U, optical bands, and at least one NIR-band turned out to be best suited to reconstruct galaxy SFHs over truely cosmological lookback times (Fritze & Lilly, 2007). Clearly, these studies need to be taken further, e.g., using more realistic SFHs in the models and including varying stellar metallicities. They are well-suited to be done at MSc or Diploma thesis levels.

Fritze & Lilly astro-ph/0701414