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Astron. Astrophys. 338, 840-842 (1998)

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3. Results

Our image of 3C287 at 5 GHz is shown in Fig. 1. Plots of self-calibrated correlated flux densities as a function of projected baseline length are shown in Fig 2. We used 5 mas circular restoring beam as there is a large gap in the uv-coverage from 25 to 100 M[FORMULA] and the phases are very noisy for the longest baselines. Despite the fact that there were no intermediate baselines present, we were able to reconstruct the source structure well at 5 mas scale. The observed flux density distribution of the source is in agreement with earlier results at 5 GHz (Fanti et al. 1989). As expected, correlated flux density on the shortest (Effelsberg-Westerbork) baseline was 1.6 Jy, about 50% of the total flux density. Model CLEAN components of our image also contain 1.6 Jy which implies that about half of the total flux density is missing from our map and probably associated with the extended, low surface brightness halo visible in Fanti et al. (1985) and Nan et al. (1988, 1991a). The source is only marginally detected on the longest baselines, and therefore no compact radio core is present at a flux density level of 5 mJy.

[FIGURE] Fig. 1. Natural weighted image of 3C287 at 5 GHz. Contour levels are -0.4, 0.4, 1, 2, 5, 10, 25, 50, 75, 99 % of the 183 mJy peak flux density. The restoring beam is 5 mas

[FIGURE] Fig. 2a and b. Correlated flux density (Jy) versus projected baseline length: a all data including baselines to Shanghai telescope, b the western EVN, 0-25 M[FORMULA] u-v range

We performed model fitting in DIFMAP using self-calibrated uv-data. The complex structure is fitted well with 7 components listed in Table 2.


[TABLE]

Table 2. Fitted elliptical Gaussian model parameters of the source structure
Notes:
S flux density, r angular separation from the centre, [FORMULA] position angle, [FORMULA] component major and minor axes, [FORMULA] component major axis position angle, agreement factor is the square root of reduced [FORMULA] (see e.g. Pearson 1995). Position angles are measured from north through east.


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© European Southern Observatory (ESO) 1998

Online publication: September 17, 1998
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