VLBA-detected sources with optical counterparts (red circles). The multi-wavelength coverage of the field is also shown: Subaru R_c, I_c, z′ filters (image), LBT U and B filters (blue solid line), LBT VYz′ filters (blue dashed line), IRAC 3.6 μm and 5.8 μm (yellow solid line), IRAC 4.5 μm and 8 μm (yellow dashed line), SDSS (black dashed line), J and K UKIDSS filters (black solid lines). The black circle denotes the area observed by XMM-Newton.