THE DARK-MATTER PROBLEM CANNOT BE SOLVED BY 10(6)-10(12)M(CIRCLE-DOT)BLACK-HOLES

We are finalising the first systematic search for gravitational multip le images separated by 50-200 milliarcseconds (mas) corresponding to a mass range similar to 10(8.5) - 10(10)M(.). In a parent sample of 158 6 radio sources selected from two VLA surveys, only 67 were found to h ave structure which could be ascribed to high magnification lensing on this scale. These were all observed with MERLIN, reducing the number that could be multiple imaged to 16. The best 7 of the remaining candi dates have been observed with the VLBA, but none were confirmed as len ses. It is unlikely that any of the remaining 9 objects is multiply im aged. If this is confirmed a limit Omega(L) < 0.05 can then be placed on 10(9) - 10(10)M(.) black holes (BH). This range can be extended to 10(6) - 10(12)M(.) by combining our work with that of others, implying that BH in this range do not contribute importantly to the total mass of the Universe.