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Association of Features

The structures of the extended features D and E shown in Figures 2 and 3 are entirely consistent with their being associated with each other as the two lobes of a large FRII double source of overall angular size 195. Both features are brightest in the regions furthest from C, contain bright (but resolved) substructure near their outer edges resembling the hot spots of FRII sources, and have their steepest brightness gradients on their outer edges. The overall length of the two lobes is the same to within 5%. Although features A and B in Figure 1 appear symmetric around feature C, the higher resolution VLA images (Figures 2 and 3) reveal them to be background sources, unrelated to NVSS 2146+82.

The northern feature (D) contains a region of enhanced emission (hot spot) at its northern extremity with about 65 mJy in an area 30'' by 18'' and an L-shaped extension to the West. The southern feature (E) has 75 mJy in a region of enhanced emission 50'' by 30'' (a "warm spot'') recessed by 10% of the distance from the core and sharp brightness gradients around its southern and western boundaries. Both regions of enhanced emission show evidence of finer, but resolved, structure in our data taken in the B configuration (see contour plots in Figure 5). Figure 3 clearly shows that the internal brightness distributions of both lobes are non-uniform, and suggest the presence of filamentary structures, again a common characteristic of FRII radio lobes at this relative resolution.

Most importantly, Figures 2, 3, and 4 also show that these lobes are linked to the central compact feature C by elongated features that are plausibly the brightest segments of a weak jet-counterjet system. These features are labeled in Figure 4.

We interpret the following features as belonging to the jet in the south lobe.

J1. This feature is clearly part of a jet that points towards the south lobe but not directly at the peak of feature E.

J2. This feature (15 from C) and feature K (14 to the north of C) are roughly symmetric in distance from C and in intensity but are not quite collinear with C. On both sides of the source the jet becomes harder to trace further into the lobe. J2 appears to be south of the C-J1 direction, suggesting a southward bend, however.

J3. This feature is plausibly a knot in the continuation of the jet into the south lobe. The lobe brightens beyond J3 and contains a diffuse ridge that is a plausible continuation of the (possibly decollimated) jet in the direction of the "warm spot'' E. The north lobe also brightens at about the same distance from C although there is no feature corresponding to J3 in the north.

Table 2 gives flux density estimates for the main features of the source. We estimate that the jet and counterjet together comprise about 1% of the total flux density of the extended lobes, a typical jet "prominence" for radio galaxies slightly above the FRI-II transition.

   

Table 2: Flux Densities

0.35 GHza 1.4 GHz 4.9 GHz 8.4 GHz tex2html_wrap_inline1346

Total

0.99 0.02 Jy 0.53 0.1 Jy -0.45 0.06
N lobe 0.43 0.01 Jy 0.24 0.05 Jy -0.42 0.07
S lobe 0.52 0.01 Jy 0.27 0.05 Jy -0.47 0.06
C 23 2 mJy 13.6 0.5 mJy 6.8 0.2 mJy 3.4 0.2 mJy -0.38 0.03
J1 1.3 0.2 mJy
J2 0.3 0.2 mJy
J3 0.8 0.2 mJy
K 0.7 0.2 mJy

a 0.35 GHz measurements are from the WENSS image.

The higher-resolution radio images provide no evidence that sources A, B, or F in Figure 1 are physically related to each other, or to C, D and E. Although none can be optically identified, we consider it likely that these are three (or more) unrelated background sources. The symmetrical alignment of A and B around C is apparently coincidental, and there is no evidence for any radio "bridge'' between these sources and component C.


next up previous
Next: Polarimetry Up: Radio Observations Previous: Radio Results


Fri Feb 4 16:02:06 EST 2000