New perspectives on cosmological shocks and magnetic fields in galaxy clusters
by
Christoph Pfrommer(Toronto)
→
Europe/Stockholm
FA31
FA31
Description
By re-assessing two different kind of radio observations, I will show that this
enables new observational windows on galaxy cluster physics. In the first part,
I will talk about the spectacular head-tail radio galaxy NGC 1265, located in
the Perseus galaxy cluster. I will present a new model that self-consistently
explains its morphology and spectrum, and accounts for the interaction
of this radio galaxy with the galaxy cluster. For the first time, we are able to
probe the detailed flow structure of an accretion shock onto a galaxy cluster.
In the second part, I address the puzzle of strongly polarized radio ridges at
spiral galaxies in the Virgo cluster. Using 3D magnetohydrodynamical simulations, I
show that these orbiting galaxies necessarily sweep up enough magnetic
field, initially woven in the cluster plasma, to build up a dynamically important
magnetic sheath - an effect well known in space physics and extensively
observed around the Earth, Mars, Venus, and comets. This magnetic draping layer
is then lit up with cosmic ray electrons from the galaxies’ stars, generating
coherent polarized emission at the galaxies’ leading edges and naturally
explaining the observations. This immediately presents a new technique for probing local
orientations and characteristic length scales of cluster magnetic
fields. Its first application gives a startling result that might point to interesting
plasma physics and hints at the thermal evolution of galaxy clusters.
