Institute for Advanced Study Informal Astrophysics Seminar
Magnetic Fields in Galaxy Clusters
Clusters of galaxies, filled with hot, magnetised plasma, are the
largest bound objects in existence and an important touchstone in understanding
the formation of structures in our Universe. Because in clusters, thermal
conduction follows field lines, magnetic fields strongly shape the cluster's
thermal history, which remains mysterious; some should have long since cooled
and collapsed. In a seemingly unrelated puzzle, recent observations of Virgo
cluster spiral galaxies imply ridges of strong, coherent magnetic fields offset
from their centre. Here I demonstrate, using 3D magneto-hydrodynamical
simulations, that such ridges are easily explained by galaxies sweeping up field
lines as they orbit inside the cluster. This magnetic drape is then literally
lit up with cosmic rays from the galaxies' stars, generating coherent polarised
emission at the galaxies' leading edges. This immediately presents a first
technique for probing local orientations and characteristic length scales of
cluster magnetic fields. The first application of this technique, mapping the
field of the Virgo cluster, gives a startling result - outside a central region,
the magnetic field is preferentially oriented radially. Our results strongly
suggest a mechanism for maintaining some clusters in a `non-cooling-core' state.
Date & Time
May 20, 2010 | 11:30am
Location
Bloomberg Hall Astrophysics LibrarySpeakers
Christoph Pfrommer
Affiliation
Canadian Institute for Theoretical Astrophysics