tokens: form the Herschel maps, into radio signal at this frequency using the Bonzini et al. (2015) relation after scaling for the magnification factor does not discard the possibility that an AGN contribution might be responsible for the remaining emission. 3 <italic>Chandra</italic> X-ray observations The galaxies SDP.9 and SDP.11 were observed by Chandra in Cycle 16, with the ACIS-S3 CCD at the aimpoint, for a total exposure time of 55.3 ks (on January 10, 2015) and 19.8 ks (on February 28 and March 23, 2015), respectively. Very faint mode was used for the event telemetry format, and ASCA grade 0, 2, 3, 4, and 6 events were used in the analysis, which has been carried out using the ciao v4.7 software. Both sources are clearly detected, with 14 counts each in the 0.5–7 keV band within a circular region of 2 ′′ radius centered on the positions reported in Sect. 2 , and 8 counts in the observed 2–7 keV band. The 0.5–7 keV Chandra images of SDP.9 and SDP.11, centered on these positions, are shown in Fig. 1 . Remarkably, the 0.5 arcsec Chandra on axis resolution is able to resolve the X-ray emission from the lensed components. The X-ray emission better matches in position the SMA data than the HST images. Fig. 1 HST/WFC3 lens-subtracted F160W images (brightness scale in μ Jy arcsec −2 , left panel ) and Chandra 0.5/7 keV images ( right panel ) of SDP.9 and SDP.11, overlaid with signal-to-noise ratio (S/N) contours at 880 μ m from the SMA (in steps of 3, 6, and 9, Bussmann et al. 2013 ; Negrello et al. 2014 ). The lownumber of detected photons significantly limits the spectral constraints that can be obtained from the X-ray analysis. To provide basic information for both sources, however, we fit the spectra extracted from the Chandra data using simplemodels (within xspec v.12.9, Arnaud 1996 ) and the Cash statistics ( Cash 1979 ), which is appropriate for low-count spectra. Fitting the spectrum of SDP.9 with a power law provides Γ = 1.1 ± 1.0, which is suggestive of obscuration. When we fixed Γ to 1.8, as is typically observed in AGN and quasars (e.g., Piconcelli et al. 2005 ), we obtained a column density of ≈ 5.2 × 10 22 cm −2 at the source redshift (3 σ upper limit of ≈ 3.3 × 10 23 cm −2 ). The observed 2–10 keV flux is ≈ 3.6 × 10 −15 erg cm −2 s −1 , and the derived apparent rest-frame 2–10 keV luminosity (corrected for absorption but not for magnification) is ≈ 3.7 × 10 43 erg s −1 . The faint flux of SDP.9 explains the non-detection of the source (with an upper limit of ≈ 10 −14 erg cm −2 s −1 in the 0.5–8 keV band) in the XMM-ATLAS survey ( Ranalli et al. 2015 ). This survey covers a 6 deg 2 area with an average exposure of 3 ks. The non-detection of the AGN in XMM-Newton suggests that it is obscured, with an estimated column density of at least 10 23 cm −2 , as observed in other bright submm galaxies ( Johnson et al. 2013 ). For SDP.11, we combined the photons of the two observations into a single spectrum. As for SDP.9, a power-law model
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