4.1.3 Fitted total intensity features

The following features of 3C31 can be accurately reproduced by our chosen fitting functions after optimization:

1. Both jets are initially faint and brighten at the beginning of the flaring region, where significant deceleration begins.
2. The brighter jet has a more centrally-peaked brightness distribution, while that of the counter-jet is much flatter.

3. The jets become more equal in brightness further from the nucleus as they decelerate (Fig. 10).
4. The on-axis sidedness ratio remains high ($\approx$13) over most of the flaring region, and drops abruptly at 5 arcsec from the nucleus. Thereafter, it declines slowly and monotonically but the main jet remains appreciably brighter than the counter-jet on-axis (Fig. 11).

The differences between the spine/shear layer and Gaussian models are at a low level. The former allows a lower emissivity in the spine, which leads to a flatter transverse intensity profile that agrees better with the data.

2002-06-13