Determining the nature of the unassociated Fermi-LAT gamma-ray sources

The Fermi satellite opened new horizons in gamma-ray astronomy with the detection of already 1451 sources in the first 11 months of science operations of the LAT instrument. While some of them are identified as gamma-ray pulsars and AGNs, other are just associated with potential gamma-ray emitters. However, many of the LAT sources have no potential association yet. Their nature is unknown and can only be investigated through multi-wavelength observations. Here we propose to map the error boxes of selected LAT sources in X-rays with XMM and in the optical with the VLT. On the basis of their X-ray/optical properties, for each LAT source we will then be able to single out the X-ray source which is a potential gamma-ray emitter.