Joe Silk (University of Oxford)

Galaxy Formation: the First Billion Years- Joe Silk Colloquium

ATNF Marsfield Lecture Theatre

Abstract

Progress has been made in understanding the origin of spiral galaxies, but elliptical galaxy formation continues to pose unresolved problems. In both cases, feedback seems to be a central issue. Why do both quiescent and star-forming disk galaxies lie on the Schmidt-Kennicutt relation? What is the role of AGN in galaxy formation?

At the centres of spheroids, one finds supermassive black holes which are occasionally fed by gas accretion from their surroundings and are visible as active galactic nuclei. Negative feedback, due to the outflow from the central black hole during its active phase, terminates the gas supply to the spheroid, thereby resulting in an old stellar population. Is there a contemporaneous phase of positive feedback during protogalaxy formation that could result in the highly efficient phase of early star formation required by the recent data?

I will discuss several of these issues.