  The Frying Pan (G315.9-0.0) is a radio supernova remnant with a peculiar
linear feature (G315.78-0.23) extending 10' radially outward from the rim of
the shell. We present radio imaging and polarization observations obtained from
the Molonglo Observatory Synthesis Telescope and the Australia Telescope
Compact Array, confirming G315.78-0.23 as a bow-shock pulsar wind nebula (PWN)
powered by the young pulsar J1437-5959. This is one of the longest pulsar tails
observed in radio and it has a physical extent over 20 pc. We found a bow-shock
stand-off distance of 0.002 pc, smallest among similar systems, suggesting a
large pulsar velocity over 1000 km/s and a high Mach number ~200. The magnetic
field geometry inferred from radio polarimetry shows a good alignment with the
tail orientation, which could be a result of high flow speed. There are also
hints that the postshock wind has a low magnetization and is dominated by
electrons and positrons in energy. This study shows that PWNe can offer a
powerful probe of their local environment, particularly for the case of a bow
shock where the parent supernova shell is also detected.
