## 3. Results## 3.1. Total intensity image of 3C 119 at 8.4-GHzThe total intensity structure at one of our three frequencies
(8.86 GHz) is shown in Fig. 1; this image has an angular
resolution of 1.6x1.2 mas. The
We estimated the flux density present in each component by summing the flux density corresponding to the component using the AIPS task IMSTAT. We present these flux density estimates for components A, B, C, and D in Table 2. Note that the observing frequencies for IF34 and IF56 are the same, as pointed out above; we can see that our flux density estimates for these two independent measurements are quite consistent, and suggest that the uncertainty in our flux density estimates for individual components is a few mJy. We calculated approximate spectral indices () for components A, B, C, and D by obtaining linear least-squares fits on a log -log plot. We used an average of the two measurements at 8.52 GHz for the flux density value at that frequency. Although our measurements span a relatively small frequency range, they have the advantage of being simultaneous in time and of having the same resolution at each frequency; for this reason, we prefer to consider only our three measurements, rather than to try to add information from previous observations at other frequencies. The resulting spectral indices are given in Table 2. We can see that the spectral index of A is close to zero, while the spectra of components B, C, and D are steep, with spectral indices . This confirms that A is the core, while B, C, and D are optically thin jet components.
## 3.2. Linear polarizationA contour map of polarized flux density
Table 3 also shows the vector sum of the polarizations for components B and C measured in each frequency channel. A very interesting point is that the sum of the milliarcsecond-scale polarized flux density for B and C averaged over the three frequencies is 242 mJy in position angle , which is quite close to the integrated polarized flux density for 3C 119 indicated by our VLA data, 238 mJy in ; this demonstrates that we have mapped essentially all the integrated polarization in the source at these frequencies, and that only a very small amount of polarized flux is located on more extended scales, beyond our VLBI images. ## 3.3. Rotation measures and intrinsic magnetic fieldsAs noted above, the two features for which significant polarization
was detected were the two knots B and C. Fig. 4 shows the
values measured for the total
polarization of these two knots at each of the three frequencies we
observed, plotted as a function of .
If variations of at our different
observing frequencies are associated with Faraday rotation, we expect
the values to form a straight line in
this plot. We can see that the
variations for both components B and C can be described well by a
dependence, indicating the presence
of Faraday rotation; the rotation measure of C (about
1590 rad/m
The rotation measures were mapped by performing a weighted fit of
the position angle to a -squared
dependence using the AIPS task RM. Fig. 5 shows the magnitude of the
rotation measure in the region where the solution errors are below
rad/m
We can now take into account the rotation measure distribution in
3C 119 to derive the intrinsic direction of the
vectors for the milliarcsecond-scale
polarization. Fig. 6 displays an
© European Southern Observatory (ESO) 1999 Online publication: March 18, 1999 |