Seeing the Magnetic fields in Galaxy Clusters

June 3, 2010 in in_the_news

Supercomputer’s New View of Virgo May Change Understanding of Cluster’s Cosmic History

TORONTO, June 3 /CNW/ – Toronto researchers have used Canada’s largest computer and knowledge from the last passage of Halley’s Comet to see for the first time the magnetic fields in a cluster of galaxies.

The results, to be announced at Canada’s largest supercomputing conference in Toronto on June 8th and in next month’s Nature Physics, change our understanding of how these largest objects in the Universe evolve.

When Halley moves through the magnetic solar wind, it wraps a sheath of strong fields around it. Magnetic fields can’t be directly seen, but their effects can; when electrons encounter magnetic fields, they begin emitting a kind of radio waves called `synchrotron radiation’.

Last year, Dr. Christoph Pfrommer, at the Canadian Institute for Theoretical Astrophysics, saw work showing strange ridges of radio emission at the edges of the galaxies in the Virgo cluster. “I soon realized what I must be seeing”, said Dr. Pfrommer. “As galaxies move through the cluster’s gas, they must drape the magnetic field — and the ridges must be that drape, lit up by electrons from the galaxies’ own stars!”


Observations, Modelled Observations, and Simulations of galaxies moving through a magnetic field (Credit: Jonathan Dursi, SciNet/CITA, University of Toronto)

Dr. Jonathan Dursi, an analyst at the University of Toronto’s SciNet, knew how to find out if this was true. “Using GPC, the largest computer in Canada, it finally became possible to do theoretical `experiments’ — to see what would happen when a galaxy runs through the cluster, and ask if the result matches what observers see.”

”]Neither researcher was prepared for the results. “I was blown away when Christoph showed me the plot”, said Dursi. “We can actually see the fields – and it’s not a tangled mess, but shoots straight outwards, making Virgo a kind of cosmic magnetic porcupine.”

“Once you see how the magnetic fields are splayed over the galaxy, you know how the original field pointed.” explained Pfrommer. “We can infer from the ridges not only that draping happens, but how the field points at those galaxies.”

Flow over a galaxy moving upwards through a galaxy cluster (Credit: Jonathan Dursi, CITA/SciNet, University of Toronto)

These results, which could explain the mystery of why half of all galaxy clusters evolve without falling into a `cooling-core state’, will be announced at this year’s High Performance Computing Symposium, Canada’s most important forum for supercomputer-powered research. More information about this work be found at

About SciNet:

SciNet is Canada’s largest supercomputer centre, providing Canadian researchers with the computational resources and expertise necessary to perform their research on scales not previously possible in Canada, from the biomedical sciences and aerospace engineering to astrophysics and climate science. More information is available at .

About HPCS2010:

The High Performance Computing Symposium is Canada’s foremost
research supercomputing conference. The 24th HPCS takes place at
the University of Toronto on June 5-9, with the theme of `Data
Intensive Computing: Across Disciplines, Across Canada’. More
information is available at .