Synchrotron emission from shocked relativistic jets. III - Models for the centimeter wave band quiescent and burst emission from 3C 279 and OT 081

Models are presented for the radio emission from the sources 3C 279 and OT 081 (1749 + 096) based on a diverging flow of synchrotron plasma with both axial and tangled magnetic field components. Outbursts are due to shocks that locally compress the field, allowing for a significant degree of polarized emission from the shocked parts of the flow. It is demonstrated that short time scale activity evident in the polarized flux is compatible with the contemporaneous, long time scale, apparently single outbursts in the total flux. This effect arises in part because high opacity restricts the duration of the polarized outbursts, keeping them distinct and in part because of the cancellation between orthogonal polarizations associated with the axial and the commpressed, tangled magnetic fields. It is estimated that the axial magnetic field contains 5-15 percent of the magnetic energy density. Model maps of 3C 279 are in qualitative agreement with VLBI maps and suggest that components on VLBI maps that are widely spaced in time, which hitherto have been assumed to a single, evolving component, are in fact a number of discrete events. 36 refs