those recently presented by Wong et al. (2017). Presenting our detailed image analysis is necessary as they are the input to the modeling of SDP.9 that will be discussed in the next section.

SDP 9 high resolution observations
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ALMA Cycle 3 observations for SDP9 were obtained in the framework of a project aiming at detecting with subarcsec resolution traces of the emission from the foreground lens (ID: 2015.1.00415 PI: Wong). A 1.875GHz-wide spectral window was centered at 268.34GHz to include the CO(6-5) emission redshifted according to the 1.577$\pm0.008$ value estimated in Bussmann et al. (2013). Three further spectral windows centered at 266.21, 254.01 and 251.51 GHz were used for continuum estimation. The native spectral resolution of the data is 31.250MHz (corresponding to $\sim35$km/s after Hanning smoothing).

Baselines as long as 16.196 km were used to reach a 0.02 arcsec resolution. A total of 4.3h, split in two execution blocks, was enough to reach 0.1$\mu$Jy sensitivity over the $\sim7.3$ GHz band used for the continuum (after flagging the channels including the CO(6-5) line).

Calibration was done manually and no major issue was found. Imaging was performed in an interactive way to apply a mask, with standard Briggs weighting scheme (robustness 