We explore the X-ray properties of the 126 sub-mm galaxies ( SMGs ) of the LABOCA survey in the CDFS and the eCDFS regions .
SMGs are believed to experience massive episodes of star-formation .
Our goal is to examine whether star-formation coexists with AGN activity , determine the fraction of highly obscured AGN and finally to obtain an idea of the dominant power-mechanism in these sources .
Using Spitzer and radio arc-second positions for the SMGs , we find 14 sources with significant X-ray detections .
For most of these there are only photometric redshifts available , with their median redshift being \sim 2.3 .
Taking into account only the CDFS area which has the deepest X-ray observations , we estimate an X-ray AGN fraction of < 26 \pm 9 % among SMGs .
The X-ray spectral properties of the majority of the X-ray AGN which are associated with SMGs are consistent with high obscuration , > 10 ^ { 23 } cm ^ { -2 } ~ { } , but there is no unambiguous evidence for the presence of Compton-thick sources .
Detailed Spectral Energy Distribution fittings show that the bulk of total IR luminosity originates in star-forming processes , although a torus component is usually present .
Finally , stacking analysis of the X-ray undetected SMGs reveals a signal in the soft ( 0.5-2 keV ) and marginally in the hard ( 2-5 keV ) X-ray band .
The hardness ratio of the stacked signal is relatively soft ( -0.40 \pm 0.10 ) corresponding to \Gamma \sim 1.6 .
This argues against a high fraction of Compton-thick sources among the X-ray undetected SMGs .