Date/Time
Date(s) - 10/01/2007
3:30 pm - 4:30 pm

Title: Preventing Star and Galaxy Formation

Speaker: Dr. Michael Balogh

Institute: University of Waterloo

Location: ABB 102

Description:

In a Universe dominated by cold dark matter, radiative cooling of gas and subsequent star formation should be a very efficient process. However, less than 10% of the baryons are in a condensed state at the present day. What generates the tremendous energy necessary to prevent overcooling? Recent observations from the Chandra and XMM X-ray telescopes have taught us a lot about this balance between heating and cooling in the centre of galaxy clusters. In particular, observations of “bubbles” filled with radio plasma suggest that black hole accretion is pumping large amounts of energy into the surrounding gas. However, I will demonstrate that this activity is insufficient to explain all the observations, and that an additional, earlier episode of heating (preheating) is required by the data. This simple model is the first to unify “cool-core” clusters with the majority of clusters, and has important consequences for our understanding of galaxy formation and evolution.