|24th of July 2017|
|Farnes et al.|
The radio source W50 is believed to be a shell-like supernova remnant
which is being re-energized by the jets from the micro-quasar SS433.
Farnes et al. used the Australia Telescope
Compact Array to make a new wide-field image of the source.
In order to cover the whole 2-degree by 3-degree extent of the supernova remnant,
a 198 pointing mosaic was observed, in each of the three most compact
array configurarions (H75, H168 and H214).
Using information from the polarisation of the radio emission,
an Rotation Measure gradient is detected
across the central region of W50, which is interpreted as a loop
magnetic field with a symmetry axis offset by about 90 degrees to the east–west
jet-alignment axis, and implying that the evolutionary processes of
both the jets and the supernova remnant must be coupled.|
The image above combines data over the frequency range from 1.4 to 3.1
GHz, with an effective bandwidth of 1.7 GHz. There are artefacts
around bright point sources due to the assumption of zero spectral
index during simultaneous imaging. A negative bowl is visible
surrounding the W50/SS433 system due to the gap in the shortest
(u,v)-spacings. The surrounding field-of-view contains several bright
extragalactic radio sources, and additionally the nearby HII region
S74 to the north-west, and one half of the shell of the Galactic SNR
candidate G38.7-1.4 to the south-west. The microquasar SS433 is
clearly visible as the bright compact source at the approximate
geometric centre of the nebula. The pseudo-colour scale is in units of
jansky per beam. The synthesized beam is shown in green to the lower
The paper describing these results has been published in Monthly Notices of the Royal Astronomical Society, vol. 467, p. 4777.