A Multifrequency Radio Study of Supernova Remnant G292.0+1.8 and Its Pulsar Wind Nebula

(Abridged) We present a detailed radio study of the young supernova remnant(SNR) G292.0+1.8 and its associated pulsar PSR J1124-5916, using the AustraliaTelescope Compact Array at observing wavelengths of 20, 13 and 6 cm. We findthat the radio morphology of the source consists of three main components: apolarized flat-spectrum central core coincident with the pulsar J1124-5916, asurrounding circular steep-spectrum plateau with sharp outer edges and,superimposed on the plateau, a series of radial filaments with spectrasignificantly flatter than their surroundings. HI absorption argues for a lowerlimit on the distance to the system of 6 kpc. The core clearly corresponds to radio emission from a pulsar wind nebulapowered by PSR J1124-5916, while the plateau represents the surrounding SNRshell. The plateau's sharp outer rim delineates the SNR's forward shock, whilethe thickness of the plateau region demonstrates that the forward and reverseshocks are well-separated. Assuming a distance of 6 kpc and an age for thesource of 2500 yr, we infer an expansion velocity for the SNR of ~1200 km/s andan ambient density ~0.9 cm^-3. We interpret the flat-spectrum radial filamentssuperimposed on the steeper-spectrum plateau as Rayleigh-Taylor unstableregions between the forward and reverse shocks of the SNR. The flat radiospectrum seen for these features results from efficient second-order Fermiacceleration in strongly amplified magnetic fields.Comment: 11 pages of text, plus 7 embedded EPS figures. Accepted to ApJ. Added missing units on x-axis of Fig