Detection of Iron Kα Emission from a Complete Sample of Submillimeter Galaxies

We present an X-ray stacking analysis of a sample of 38 submillimeter galaxies with <z>=2.6 discovered at >4σ significance in the Lockman Hole North with the MAMBO array. We find a 5σ detection in the stacked soft band (0.5-2.0 keV) image, and no significant detection in the hard band (2.0-8 keV). We also perform rest-frame spectral stacking based on spectroscopic and photometric redshifts and find a ~4σ detection of Fe Kα emission with an equivalent width of EW>1 keV. The centroid of the Fe Kα emission lies near 6.7 keV, indicating a possible contribution from highly ionized Fe XXV or Fe XXVI; there is also a slight indication that the line emission is more spatially extended than the X-ray continuum. This is the first X-ray analysis of a complete, flux-limited sample of SMGs with statistically robust radio counterparts.