VSOP Survey Images

Because the maximum distance between Halca and ground radio telescopes is much greater than can be achieved with ground radio telescopes alone, the resolution of images made with survey data is typically two to three times better than images made with ground-based VLBI. Images of survey sources can be constructed when the number of co-observing ground telescopes exceeds a minimum number (two or three, depending on the quality of the a-priori telescope gain and system temperature information). High resolution imaging of the AGN cores is crucial to understanding the nature of the emission mechanism "powering" these AGN. Using Halca, images of AGN cores with sub-mas resolution can be constructed. For relatively nearby AGN ( Z < 1), this corresponds to a linear distance on the order of 10pc.

Four images of VSOP survey sources that were at least partially resolved out are shown above. The resolution of the images in all four cases in roughly 1.0 mas X 0.3 mas. The sources on the upper left and right are QSOs, while the lower left source is a BL-Lac, and the lower right source is a radio-galaxy. Redshifts for these sources range from 0.35 to 2.69.

Overlayed on these images are contours made by subtracting the data from the Space-ground baselines. In all cases, the resolution is considerably reduced. For the lower right source, when Halca was subtracted from the array, the remaining three ground radio telescopes (Hobart and Mopra in Australia, and Hartebeesthoek in South Africa) formed nearly an East-West array. This resulted in the exceptionally bad resolution seen in the North-South direction.

Additional space VLBI images from general observing time proposals can be found on the ISAS web site.