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S9: Galaxy Evolution : the key for Galaxy Formation

Rationale :
The basic physics of galaxy formation and evolution is one of the most important unsolved problems in Astrophysics and Cosmology. The most popular structure formation paradigm, based on the Hierarchical Cold Dark Matter (CDM) scenario, is based on the growth of small (~105 Mʘ) initial fluctuations requiring at least ten Gigayears to reach the present mass of normal galaxies up to ~1011-12 Mʘ. This model was successful to explain a variety of observational data from the temperature anisotropies of the cosmic microwave background, the clustering of galaxies. Simultaneously, the discovery of massive galaxies and supermassive black holes at early epochs (z>3) implicitly requires huge initial fluctuations and the dominance of dissipative gravitation or rapid merging at early epochs. Other physics such as dynamical friction in dense media, intense dissipations from ionized gas and dust, also play their role depending on environment density and nature.

From the historical CDM article by Blumenthal et al, 1984, a large variety of galaxy formation models using a physical approach based on semi-analytical recipes and dark matter numerical simulations, carried out on large parallel supercomputers, were built on this cosmology pattern and a limited set of physical parameters. They produced a general picture of collapsing objects out of primordial density fluctuations. They tentatively interpret the extragalactic background light (EBL) as the relic emission due to galaxy formation and accretion process since the recombination down to the re-ionization phase and the formation of primeval galaxies. The main uncertainties of such models are masses of dark haloes, the recipe of star formation efficiency in mergers and the role of feedback from AGN or gas exchanges.

Another approach is based on the evolutionary codes allowing to interpret the signatures of galaxy evolution by types taking into account the environment as well as passive evolution of stars, absorption and emission of gas and dust in coherency with metal enrichment. Evolutionary codes produced significant successes for analyses of the largest and deepest galaxy surveys. They also are fruitful to understand the huge amount of data resulting from fantastic advances in observational instrumentation and data mining. The large extent of the wavelength coverage allow to constrain the young to past star formation history, masses and velocities over an unprecedented redshift extent ( z=0 to 6) reaching several Gigayear of ages. All these parameters are traced by individual objects (radio galaxies, Lyman Break Galaxies, Damped Lyman alpha systems) or in populations through the evolution of galaxy luminosity and mass functions in larger and deeper surveys. Gamma-Ray Bursts as distant hypernovae and X-ray surveys revealing populations of QSOs and radio galaxies from the High Energy domains traces early populations of energetic photons and possibly associated starbursts. In the UV-visible-nearIR, deep surveys give informations on stellar masses. Far-infrared and submm observations revealed the cosmic infrared background as well as the puzzling populations of Ultra Luminous InfraRed Galaxies (ULIRG) and powerful Submm Galaxies (SMG) with ISO, Spitzer. Now the satellite Herschel and the ALMA array, currently opened up to the community, aim the possible detection of galaxy-sized objects while polarization, the collapse of primordial density fluctuations and re-ionization with PLANCK will complete our knowledge of the evolution domain up to formation.

The main objectives of the session is to confront observers and model builders towards a constructive scheme of the galaxy distributions by types at all redshifts in the frame of the evolving universe. The compatibility of all models with observations will be presented as well as the problems showing the difference of model physics. The root of the challenge is to point out the key parameters: mass, luminosity or velocity dispersion, the evolution of which would explain the driving process of galaxy formation and evolution in dark matter haloes. The variation time scale of parameters and when possible, their calibrators are determined for all types: from the Hubble sequence populations, including our Galaxy and dwarfs at redshift z=0, up to intermediate and high redshifts (z>4). The evolution of galaxy luminosity and mass functions by types and their correlations with black hole masses also will be considered.

Several points need discussions about the separation of multiple components in deep surveys, the rapid fading of surface brightness favoring bulges and nuclei at high redshifts, the disentangling of evolution/cosmology signatures, the unicity/multiplicity of solutions, the spatial and spectral low/high resolution confusion.

The next generation of instruments (HERSCHEL, ALMA, GAIA) as the future research facilities of its era, such as the Expanded Very Large Array (EVLA), James Webb Space Telescope (JWST), Thirty Metre Telescope (TMT), European Extremely Large Telescope (E-ELT), and Square Kilometer Array (SKA) will provide a complete picture of the physics of galaxies in coherency with the Cosmology paradigm.

The following topics will be covered:
  • Star formation Activity: calibration and coherency of tracers (IR/UV/SN/GRB)
  • Evolution of masses, metals, dust to z>6: Constraints for hierarchical/gravitation models
  • Main divergences of numerical and evolutionary models with observations
  • Mass and velocity correlations with supermassive Black Holes
  • Galaxies in populations through deep surveys
  • Re-ionization from UV sources, perspectives with Planck
Contact: rocca@iap.fr

Provisional list of invited speakers include:
C. Carilli (NRAO, USA), P. Cox (IRAM, France) , A. Klypin (New Mexico, USA), de Blok (Cape Town, SA), Yuexeng Li (CfA, USA), Kormendy (Univ. Texas, USA) , P. Andreani (ESO, Germany) , Peter Capak (Caltech, Pasadena), N. Gnedin (Particule Astrophys. Center, Chicago), F. Bouchet(IAP, France), D. Stern (JPL, USA), A. Kravtsov (Chicago), O. S’ilchenko (Moscow), M. Kontizas (U. Athens, Greece), S.Gottloeber (IAP,Germany), J.Schaye (Leiden Univ).

SOC: B. Rocca-Volmerange (IAP, France), A. Dorochkevich(Astro space Center, Moscow), C. De Breuck (ESO, Germany)