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Today's Colloquium: Probing the Galactic Magnetic Field using the Gum Nebula

Submitter: Cormac Purcell (Sydney Uni)
Description: The Gum Nebula is a 36 degree wide shell-like emission nebula at a distance of only 450 pc. It has been hypothesised to be an old supernova remnant, fossil HII region, wind-blown bubble, or combination of multiple objects.

Here we investigate the magneto-ionic properties of the nebula and its impact on the ISM using data from recent surveys: radio-continuum data from the NRAO VLA and S-band Parkes All Sky Surveys, and H-alpha data from the Southern H-Alpha Sky Survey Atlas. By analysing rotation measures through the nebula and by fitting a simple model, we are able to measure the geometry and strength of the local ordered magnetic field. The fitted compression factor at the edge of the nebula points to its likely origin.

The nebula is also useful as a probe of the magnetic field on parsec scales and the fitted value of local magnetic pitch-angle represents a significant deviation from the median orientation on kiloparsec scales. I discuss the implications for Galactic structure and plans for expanded analysis in the era of the SKA.
Copyright: Cormac Purcell (Sydney Uni)
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