Detection of X-ray Emission from Gravitationally Lensed Submillimeter Sources in the Field of Abell

We report the detection by Chandra of SMM J02399−0134 and SMM J02399−0136, two distant (z = 1.06 and z = 2.81, respectively) submillimeter sources gravitationally magnified by the galaxy cluster Abell 370. These are high-significance (> 7σ) X-ray detections of the high-redshift submillimeter source population. The X-ray positions are coincident with the optical positions to within one arcsecond. The X-ray spectra, while of low signal-to-noise ratio, are quite hard. Absorbed power law models with fixed photon indices of Γ = 2.0 imply local absorbing columns > 2×10 cm and unabsorbed luminosities > 10 erg s in both sources. These results imply that nuclear activity is responsible for the bulk of the luminosity in SMM J02399−0134, and for at least 20% of the luminosity of SMM J02399−0136, consistent with previous optical observations. We also place an upper limit on the X-ray flux of a third submillimeter source, SMM J02400−0134. Considered together with previously published Chandra upper limits on X-ray flux from submillimeter sources, our results imply that 20 −16 % of submillimeter sources exhibit X-ray emission from AGN (90% confidence), consistent with expectations of their contribution to the diffuse X-ray background. Subject headings: galaxies: active—galaxies: clusters: individual (Abell 370)—submillimeter—X-rays: