VLBA flux

For each detected source at each band, two estimates of correlated flux density were computed: one integrated over the entire image (total CLEAN flux density) and another averaged only over the spatial frequencies > 45 Mega-lambda at S-band and > 170 Mega-lambda at X-band, which corresponds to the range [0.7, 1.0] of the maximum spatial frequencies of the VLBA. The latter estimate characterizes the flux density of unresolved components. Errors of our estimates of total correlated flux density of sources brighter than 100 mJy are determined mainly by the accuracy of amplitude calibration, which for the VLBA is at the level of 5% at 1-10 GHz. The contribution of fringe amplitude errors is significant for sources with flux density < 100 mJy. The error of correlated flux density for this group of sources is about 10%. It should be noted that in the case of a source with asymmetric extended structure the estimate of the correlated flux density from unresolved components may be biased due to a significant non-uniformity of uv coverage at long spacings.