Scientific Rationale

The classi fication of galaxies according to their shape and appearance is one of the earliest, and yet most fundamental, tools of extragalactic astronomy. From the pioneering efforts by Hubble, Sandage and van den Bergh, to the most recent and sophisticated studies, the goal has remained the same: to link the properties of the different structural components to the underlying physical mechanisms that govern their formation and evolution.

Recent years have witnessed an enormous progress in the knowledge of morphological and structural properties of galaxies at different cosmic times. For instance, it is now clear that massive ellipticals as a population substantially increased their mean size during the last 8 Gyr. Galaxy bulges have emerged as a complex family of non-homologous systems, whose evolution appears to be tightly tied to that of their host galaxy and their super-massive black holes. A signi ficant fraction of galaxy disks exhibit systematic deviations at their outer parts from the classic exponential pro les, a feature not yet fully understood. The well-known galaxy colour bimodality is best explained in terms of the relative contribution of the diff erent structural components. Perhaps more fundamental, it is now well established that morphology and structure, though closely linked, are two di fferent galaxy properties - but it is yet unclear what role environment and internal galaxy kinematics play in this relation.

The reasons for these improvements are threefold. Our understanding of the relevant physical processes has greatly developed with the aid of high resolution, realistic numerical simulations. From an observational point of view, multiwavelength surveys probing large volumes at both low (e.g., SDSS) and high redshift (e.g., GOODS, COSMOS) have produced unprecedented amounts of high-quality data for statistically signifi cant samples. Furthermore, analysis methods have extraordinarily developed from the simple visual classifi cations to very detailed quantitative measurements of both morphological and structural parameters. This is in fact a natural evolution, since any optimal classifi cation system should be as objective (i.e., reproducible) as possible.

The forthcoming years appear even more promising, as a wealth of data is expected in the nearby future from already existing (e.g., VISTA, VST) and upcoming facilities and instrumentation (e.g., LSST, MUSE, DECam) and their associated large surveys. Moreover, the E-ELT will provide a major breakthrough in the study of high redshift galaxies thanks to its diffraction-limited NIR imaging, resulting in sub-kpc resolutions for objects at z ~ 2. The increase in both sample size and detail level will translate into new challenges and difficulties that must be overcome.

Therefore, the time is ripe for a conference that brings together world-class experts to discuss the most recent advances in the understanding of galaxy structure and morphology — with a special emphasis on the latest observational results and their interpretation, and a review of state-of-the-art tools and analysis methods. The list of topics to be covered should include:

  • The underlying physics of structure and morphology
    • The roles of environment, galaxy mass and internal kinematics.
    • Evolution over cosmic times.
  • Structure and morphology of disk galaxies and the Milky Way
    • Disks: scaling relations, thin and thick disks, truncations and anti-truncations.
    • Bulges: families of bulges, their scaling relations and their SMBHs.
    • Bars: structural properties and bar frequency.
  • Structure and morphology of spheroidals
    • Morphology and size evolution.
    • Shape, inner structure and relation to SMBHs.
    • The shape and structure of early-type dwarfs.
    • The structural properties of faint Local Group satellites.
  • Tools and analysis methods
    • Automatization and the complexity of model selection.
    • Estimation of uncertainties, robustness and reproducibility.


The meeting is intended to be highly participative, with substantial time devoted to discussions.

This ESO Workshop should set the basis for the study of galaxy structure and morphology in the next decade.