Polarimetry of a Galactic Synchrotron Jet

UKIRT has always been proud of its ability to measure polarisation from celestial objects, via the use of the IRPOL polarimetry module (supplied by the University of Hertfordshire, England). In the above example, the emission from the extragalactic jet associated with M87 (see this page for more details on M87) is seen to be strongly polarised. The size of the red lines or "vectors" illustrates the percentage of light emitted that is polarised; the orientation of the red vectors represents the polarisation angle, that is, the orientation of the "electric vector" axes of the light waves emitted from the jet. The emission derives from ions and electrons that spiral around strong magnetic field lines that are aligned with the axis of this remarkable, galaxy-sized jet. Note how the direction of the polarisation vectors change considerably from knot to knot along the jet, as the jet twists and turns. The nucleus of the galaxy is, by compariosn, only very weakly polarised.

Our thanks to Lerotodi Leeuw, T.V. Cawthorne, and Ian Robson for allowing us to show these data.