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Understanding the early phases of assembly and formation of galaxies is a challenge. We deal with a complex scenario, where mass accretion and dissipative collapse played important roles, leading to the formation of different structural components. In particular, stellar halos, with their Gyrs long dynamical times, maintain more clearly the fossil records of the events that led to their formation. Galaxy halos are ubiquitous in luminous galaxies and we now know that they extend out to hundred kiloparsec, that they have complex morphologies with a complicated web of tails and substructures, and that they harbor multiple stellar components, with different abundances and star formation histories.
To understand how the galactic assembly took place we need to combine observations (information on substructures, smooth components, the dynamical status, the chemical abundances, the morphology of halos both nearby and far) with theoretical modelling.
The IAU symposium 317 at the XXIX IAU GA in 2015 will take place at the verge of a revolution that is brought about by the availability of unprecedent new data, provided by the Gaia satellite, space telescopes (HST, Spitzer) and by a number of large ground-based spectroscopic and photometric surveys of the Milky Way, M31 and external galaxies. The diverse and complementary expertise of the astronomers attending the IAU general assembly provides the possibility of a quantum leap in our understanding of `how and when' our Galaxy and the other halos formed.
To attend to the IAU Symposium 317 and submit abstracts for oral or poster contributions, please proceed to the IAU XXIX GA official web site here