A radio/X-ray comparison of the Vela X region

We present a VLA image of the Vela X region, a nebula thought to be powered by the young pulsar B0833-45, at a resolution of approximately 1.'3. The morphology of this synchrotron nebula is dominated by a network of fine, overlapping linear filaments. The brightest filament lies just south of PSR B0833-45 and can be traced to the center of Vela X, 40' away. This radio filament appears to be the counterpart of an X-ray feature first detected by Markwardt & Ogelman (1995). Rather than a one-to-one position alignment between them, the radio filament is systematically offset and traces the eastern boundary of the X-ray feature. We consider several models for the origin of the radio filament and its relation to the X-ray feature. At present, the data cannot distinguish between whether the radio emission is due to electrons accelerated in situ or whether the radio emission results from the compression of the relativistic pulsar wind. We suggest several possible observations to enable us to distinguish which hypothesis is correct.