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Symposium 241

Scientific Rationale

With the new generation of 8-10m telescopes coming on-line in the last decade, we are seeing a dramatic improvement in the quality of the observations in astronomy, leading to huge advances in our knowledge of stars and galaxies. Stellar populations can be considered as the building blocks of galaxies and therefore their study is crucial to understand these systems. They are direct tracers of the star formation history, the chemical enrichment and the assembly of galaxies in the Universe. If we can interpret the observed properties of nearby stellar populations in terms of physical parameters such as age, star formation history, metallicity and dust content, we will be able to elucidate the processes that were important in the formation of the galaxies we see today. In fact stellar population studies are providing important clues and among the strongest constraints to current galaxy formation scenarios.

At present, theoretical models in several areas are catching up with data, rather than data catching up with models, as was the case in the past. It is therefore crucial that theorists meet observers, to be able to improve the models and maximize our understanding of stellar populations in the near and distant Universe. The new instruments on the ground and in space are revolutionizing stellar population studies. The fact that we are starting to be able to resolve stars up to the distance of the Virgo Cluster means that it is now possible to rigorously compare and calibrate the analysis of integrated light with the study of resolved stellar populations. At this point, researchers of resolved stellar populations and those working with integrated light, two important areas of research that have grown separately, are now able to unite their efforts. A new generation of instruments, such as multi-object and integral field spectrographs is making it much easier to complete surveys of millions of objects up to large distances and look-back times. These new observing facilities are now enabling us to use previously less explored wavelength regions, which are crucial for understanding the physics of stars and galaxies. Furthermore the recent development of Virtual Observatories is making it increasingly easy for astronomers to obtain the data they need. Now efforts will be required to maximize the opportunities offered by this flow of data for a deeper understanding of relevant stellar population parameters.

In this conference we will discuss the ingredients of the best stellar population models available at present, and rigorously compare them to new data, forcing theorists to develop more refined models and more efficient methods to derive the physical parameters of stellar populations, both for the nearby and for the distant universe. We will cover resolved and unresolved stellar populations from stellar clusters in our galaxy to distant galaxies. However, the main aim is to identify the main problems affecting these studies and to provide the best approaches to follow on the basis of self-consistent calibrations. The time is ripe for theorists to meet observers and for young astronomers to learn from experienced researchers in the field of stellar populations.

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