Detection of iron Kα emission from a complete sample of submillimeter galaxies

Abstract

We present an X-ray stacking analysis of a sample of 38 submillimeter galaxies (SMGs) 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. © 2012. The American Astronomical Society. All rights reserved..