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.
References:
Fritze & Lilly astro-ph/0701414