Richard Ellis
Professor of Astronomy and Director of  Palomar Observatory
Caltech
 

Edwin Hubble's galaxy classification scheme, introduced
in 1926, remains in widespread use. However, the physical
origin of the various galaxy types remains unclear. Moreover,
structure formation models suggest that galaxies undergo
transformations as a result of various environmental processes.
Astronomers are now seeking a unified evolutionary picture that
accounts for such changes in the context of predicted mass
assembly histories. Hubble Space Telescope data, taken in
conjunction with ground-based surveys, enables us to make
progress towards a more detailed understanding of how
galaxies form and evolve.