Scientific Rationale

Observational information on the morphology of galaxies and its dependence on environment is routinely becoming available for galaxies up to redshift two and beyond, and matched samples at low and high redshift allow the study of the evolution of many physical properties of galaxies for most of the history of our Universe in unprecedented detail. Galaxies appear quite different at high redshifts, clumpy and perturbed, with thick disks, and quite far from the current Hubble sequence.

At the same time, thanks to a well established paradigm of cosmological structure formation, many of the boundary conditions for galaxy formation are now fixed. Modern simulations based on this paradigm have established a tight connection between the geometry and dynamics of the large scale structure of matter on the one hand, and the evolution of the physical properties of forming galaxies on the other. Key questions formulated many decades ago are nevertheless not satisfactorily answered. What are the main drivers determining the morphology of galaxies which are responsible for establishing the Hubble sequence. When did this happen? To what extent should numerical simulations be trusted to help answering these questions?

The purpose of this conference is to take stock of recent progress of both observation and simulations in order to understand the origin and evolution of the Hubble sequence within an increasingly well defined cosmological paradigm for galaxy formation. The discussion at the conference will focus on the interaction of galaxies with their environment and on the influence of the cosmic web and large scale structure dynamics. Some of the discussion will be dedicated to an critical assessment of the role of cold flows, merger/interaction history, star formation history and stellar feedback, secular evolution due to internal perturbations driven by instabilities, and nuclear activity and AGN feedback. The conference thereby aims at helping to disentangle the relative effect of all these interconnected influences on galaxy morphology which will be crucial for a proper understanding of the origin of the Hubble sequence.

Scientific Topics

How much of the chemo-dynamical evolution of galaxies is driven by environment?

Nurture versus nature: how important is the cosmic web down to galactic scales?

How and when was the present Hubble sequence of galaxies established?

What determines galaxy morphologies in cosmological structure formation scenarios?

What physical galaxy-transforming processes dominate morphology: galaxy interactions and mergers, external accretion and outflows, secular evolution?

What are these processes' respective roles in shaping disks, bulges or spheroids?

Does it make sense to model morphology if stellar mass is wrong?

What is the efficiency of star formation through the Hubble time?

When and how is feedback (star formation and/or AGN) relevant for morphology?²

What forms a bulge, a disc, an elliptical? Is it the same process at low and high redshift?