Optical spectroscopy of MIR selected AGN candidates

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Among 3000 high galactic latitude sources detected by the ISOCAM Parallel Survey at 6.7 µm we have discovered a population of extremely infrared, mostly unknown objects. Various colour criteria from optical and 2MASS wavebands and the comparison with known object types leads us to suggest that we have found AGN with a pronounced mid-IR emission of nuclear dust at T > 100 K. If true, this technique will provide a new AGN selection criterion, not affected by extinction. As a consequence, we estimate that the number counts of AGN have to be revised dramatically. In order to verify our hypothesis, we have selected 120 of our AGN candidates with yet unknown classification. We wish to perform a spectroscopic survey of these objects in order to i) establish their nature as AGN and ii) to determine the fraction of type 1 and 2 AGN among this MIR selected sample.